JP2013035998A - Low fogging leather - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing natural leather for an automobile seat that is manufactured after a pretreatment process before tanning a hide, followed by a tanning process and a shaving process, a series of processes of retanning, dyeing and stuffing processes, and a drying process, wherein a coating film comprising a base coat layer, a color coat layer, and a top coat layer is formed; and to provide the natural leather for an automobile seat that is such that the fogging generation amount can be suppressed by at most a certain level even in a hot condition in a composite to which a urethane pad (cushioning material for an automobile seat) is attached.SOLUTION: A composition includes: 2-12 wt.% of vegetable tannin based on a shaving leather weight; synthetic tannin of the amount in which the total with the vegetable tannin becomes 7-25 wt.%; 2-12 wt.% of a resin tanning agent; and 6-14 wt.% of a fatliquor, as a treating agent of a series of processes of retanning, dyeing, and stuffing processes, wherein the composition is used which satisfies Formula (I): (synthetic tannin)+(fatliquor)-(vegetable tannin)≤22.0.

Description

The present invention relates to low fogging leather.

Fogging is a phenomenon in which a material placed in a high-temperature environment generates a gaseous chemical substance under the influence of heat, adheres to the surface of the glass, cools and aggregates, and the glass becomes cloudy. When targeting the inside of a car, it is a problem that chemical substances volatilized from the car interior material cause fogging on the windshield, mainly on the windshield, obstructing the driver's view and making it difficult to see the outside state. Has been.
Although it is said that no serious situation has occurred, it is assumed that if extreme cases are anticipated, there is a risk that driving may pose a risk and that it may lead to an accident. Measures have been taken to prevent outbreaks.

Automakers and material manufacturers that provide interior goods have taken measures against fogging.
According to a report from a company that manufactures automobile seats that use natural leather as the skin material, in the process of manufacturing natural leather for automobile seats, it is the presence of lipids derived from raw leather and chemicals used in the manufacturing process. States that fogging occurs due to the use of ammonium compounds such as ammonium chloride and ammonium formate (decalcification process / neutralization process), greasing agents, surfactants, etc. Patent document 1 Journal of the Society of Leatech Technologists and Chemists, Vol. 83, p.149? 153, 1998).
For this reason, measures to prevent the occurrence of fogging in natural leather for automobile seats are to eliminate the use of ammonium chloride in the manufacturing process, and to develop and use a low-fogging greasing agent. It is mainly performed to manage the generated gas that does not exceed a certain standard.

Greasing agents used in the production of natural leather are considered to be a major cause of fogging, and greasing agents that are less prone to fogging have been developed.
EP 498634 A2 (Patent Document 1) discloses a special polymer for producing leather with less fogging, and at least one hydrophobic monomer substantially free of organic solvent and as a main component, and a small amount of at least There are amphiphilic copolymers formed from one type of hydrophilic monomer.
Of course, problems arise in copolymerization because the monomers used have different hydrophilicity. Due to the inherent reverse nature of monomer-to-monomer solubility, expensive reprocessing is required to break down the residual monomer. Problems such as the possibility of raising wastewater problems in leather processing operations have been pointed out.
EP466392B1 (Patent Document 2) discloses a method for producing a polymer containing a hydrophobic pendant group and an alkoxylated pendant group into a derivative after polymerizing the polymer. Polymers are prepared from conventional monomers such as acrylamide and / or acrylic acid by conventional polymerization methods, followed by using a mixture of primary amines with hydrophobic groups and alkoxylated primary or secondary amines. A derivative is formed. The polymers described are used as thickeners and antifouling agents.
WO 98/10103 (Patent Document 3) discloses that a polymeric greasing agent can be copolymerized first with acrylic acid and / or methacrylic acid and / or their acyl chlorides and / or their anhydrides. Disclosed is a method of production by a method of polymerizing with a water-soluble monomer and a copolymerizable water-insoluble monomer and then reacting the resulting polymer with an amine.
In order to produce a greasing agent composition with less fogging and a high exhaustion rate, “Component A which is a C ₆ -C ₁₄ -alkanol alkoxylated with 12 AO units or a mixture of a plurality of such alkanols” , 15 to 30 _C was alkoxylated with AO units 12 _{-C 24} - component B is a mixture of fatty alcohols, and 40 to 100 amino _C 12 alkoxylated with AO units _{-C 24} - fatty alcohols An emulsifier composition comprising component C which is a mixture of the above and a suitable greasing composition as described above, and a method of using the emulsifier composition and the greasing composition obtained in the manufacture of leather " Patent Document 4: Japanese Translation of PCT International Publication No. 2005-502458, BSF), one kind of hydrophilic monomer (acid and anhydride such as acrylic acid and methacrylic acid, base substitution (meta Acrylate, selected from the group consisting of (meth) acrylamides) and 10 to 50% by weight and hydrophobic comonomers (alkyl (meth) acrylates, primary alkenes, vinyl esters of alkyl carboxylic acids, and mixtures thereof) And a method for treating leather produced from 50 to 90% by weight (which is at least one monomer) (Patent Document 5: Japanese Patent Laid-Open No. 05-59399, US Pat. No. 5,348,807, Rohm and Haas).
At least one of the carboxyl groups (—CO ₂ H) present in the dimer or trimer fatty acid is —CH ₂ N [CH ₂ —CH ₂ —CO ₂ H] ₂ and / or —CH ₂ N [CH ₂ —CH (CH ₃ ) Dimer and / or trimer aminopropionic acid obtained by conversion to —CO ₂ H] ₂ group. Compound (I) is used in the form of an acid or an alkali metal salt, alkaline earth metal salt, ammonium salt, alkylammonium salt or alkanolammonium salt thereof. These aminopropionic acids are suitable for leather oil finishing. Leather treated in this way is particularly distinguished by washing and cleaning, fogging and their good resistance to water (Patent Document 6: JP 09-510490). The alkylenediaminotetrapropionic acid having a specific structure is suitable for oiling finishing of leather. Leather treated in this way is particularly distinguished by their good resistance to washing and cleaning, fogging and the use of greasing agents for water (patent document 7: JP 09-510491). The major feature is that a substance that suppresses the generation of undesirable substances is used. The above-mentioned method is a method of changing the treatment agent to solve the fogging problem by paying attention to a specific treatment step that is considered only for the greasing agent that has been used.

On the other hand, the leather manufacturing process is essentially a multi-step process, and each of these processes is larger or smaller, and there is a cause of fogging of the natural leather for automobile seats, which is the final product. Can be considered. In this case, there is an idea that by performing the process of each process with certainty, the process of each process process is sufficiently executed, and as a result, the generation of the vogging substance can be suppressed.
From this viewpoint, the present inventors proceeded with the study on the premise that it is necessary to consider the conditions for all processes for producing leather using leather as a starting material, and disclosed in Japanese Unexamined Patent Publication No. 2007-70487, “Leather Materials and The invention of “Leather Material Manufacturing Method” (Patent Document 8, Midori Hokuyo / Toyota Motor) was completed. This is a leather material suitable for adhesion to an instrument panel or the like that is less prone to fogging and has a small heat shrinkage rate, and has the following features.
“(1) Tanning and re-tanning use synthetic tannins. (2) Avoid the use of greasing agents that cause fogging and offensive odors, and use softening agents. (3) Antioxidants in the greasing process. To suppress the generation of volatile substances and offensive odor due to oxidative degradation of lipids, etc. (4) Shrink in advance by heat treatment, (5) Resin is applied to the back surface to block the release of volatile substances This reduces heat shrinkage and reduces volatile substances to suppress fogging even in parts where the usage environment is severe, and further suppresses the generation of odors due to oxidation. "
The features of the invention are summarized as follows.
“An animal-derived raw skin that has been subjected to a tanning treatment with a synthetic tannin and a softening treatment with a softening agent, and an antioxidant is contained in the fiber of the raw hide, and the color difference ΔE after coating is 100 to 100 or less. Leather material heat-treated at 120 ° C. "
The problem of the present invention is that it cannot be applied to chrome-tanned leather because it has a problem of reducing the heat shrinkage rate, and the finished leather product has a hard texture.

An automobile seat has a base made by covering a frame structure assembled by welding bent steel pipes or pressed steel plates with a foamed polyurethane pad (hereinafter referred to as urethane pad). The urethane pad creates a seat shape and serves as a cushioning material. When natural leather is used as a skin material for automobile seats, natural leather is attached to the surface of this urethane pad. The attachment is performed by covering the urethane pad while stretching the natural leather that is sewn according to the shape of the seat.
As for the fogging of natural leather for automobile seats, the inventor himself was surprised by attaching natural leather produced for automobile seats to urethane pads on a small part of automobile seats made of natural leather obtained from general-purpose chrome leather. Only when the composite is used, there is a problem that fogging occurs.
In order to resolve the question that the cause of the failure is that the manufacturing process is not performed in accordance with the determined processing conditions, the manufacturing process conditions are implemented according to the specified conditions. Reproduce the natural leather in the state, the treatment agent used in the leather treatment process is not fixed inside the leather, it remains as an unreacted substance in the free state, and the decomposition products generated after the treatment are In consideration of the case where they remain without being removed from the leather body and are involved in the occurrence of fogging, the leather was washed with water. Although the water-based leather was partially effective, it was not effective at all, and it was not possible to conclude that sufficient measures could be established only by washing the leather with water.
Therefore, returning to the beginning, it was necessary to confirm the state and conditions of fogging from the complex, and the following points were examined.
A composite with a urethane pad attached to leather in order to investigate the cause of fogging generated from a composite with natural leather attached to a urethane pad on a small part of a car seat made from general-purpose chrome leather. In a fogging environment, a causative substance is generated and adhered to the glass surface as an adhering substance, and this is analyzed to identify the causative substance causing the fogging. For new automobile seats by identifying the causative substances and examining improvement measures to change the substances to be used, by preventing the generation of substances that cause fogging from natural leather for automobile seats attached to urethane pads We decided to develop natural leather.
The natural leather for automobile seats manufactured by the present inventors is a product premised on being flexible and having the best quality in terms of feel. By examining the conditions of each manufacturing process of this product in detail and executing the conditions reliably, the state of generating fogging from the composite and the condition for confirming the conditions from the natural leather for automobile seats attached to the urethane pad, We thought that it was possible to develop new natural leather for automobile seats that can prevent the generation of fogging substances.
Under this assumption, we decided to identify the causative substances that cause fogging. For new automobile seats that identify the causative substances and study improvement measures to change the substances used to prevent the generation of substances that cause fogging from natural leather for automobile seats attached to urethane pads. We decided to develop natural leather.

Journal of the Society of Laser Technologies and Chemists, Vol. 83, p. 149-153, 1998

EP498634A2 publication EP466392B1 publication WO98 / 10103 Publication JP 2005-502458 A JP 05-59399 A, US Pat. No. 5,348,807 Japanese National Patent Publication No. 09-510490 JP-T 09-510491 JP 2007-70487 A

Problems to be solved by the present invention include a pretreatment step before tanning, a tanning step, a shaving step, a retanning / dyeing / greasing step, and a drying step, followed by a base coat layer, a color coat layer, and a top coat layer Natural leather for automobile seats produced by forming a coating film made of the above, and natural leather for automobile seats and urethane pads (cushioning materials for automobile seats) that can suppress the occurrence of fogging below a certain level even under high temperature conditions ) Is provided with a composite body with natural leather for automobile seats.

Means to solve the problem

The present inventors tackled the above-mentioned problem and solved the above-mentioned problem as follows.
(1) Setting of fogging performance evaluation criteria A new fogging performance evaluation criteria was set.
When leather is mounted on an actual vehicle as an automobile seat skin, it is placed on the urethane pad, which is a cushioning material, so that this situation is reflected and the fogging performance is evaluated with the leather and urethane pad combined. . Specifically, it is as follows.
(A) Evaluation of agglomeration amount of volatile matter on glass plate A windscreen fogging tester WF-2 (manufactured by Suga Test Instruments Co., Ltd.) was used. In a cylindrical beaker (diameter 90 mm, height 190 mm), put a urethane pad 80 mm in diameter x 40 mm in height and leather 80 mm in diameter with the leather facing up, and use a glass plate (110 x 110 x 3 mm) The cap was put in an oil bath kept at 100 ° C. and heated for 72 hours. The glass plate was cooled by applying a cooling device set to 20 ° C. from above.
(B) Adoption of glass plate reflectance measuring device The reflectance of the glass plate was measured using a gloss measuring device REFO60 (manufactured by HACH LANGE, Germany).
(C) Setting of reference value If the measurement result of the reflectance by the reflectance measuring device for the glass plate is 80% or more, it can be said that fogging does not occur in the actual vehicle (it does not cause a problem even if it occurs). ).
(D) The measured value of the composite of the conventional leather for automobile seats and the urethane pad considered as a problem is as follows.
General-purpose leather 72.0%
Semi-aniline leather 61.3%
From the point of view of numerical values, these are natural leathers that may cause fogging.
(2) Elucidation of fogging-causing substances The substances that evaporate from the composite of natural leather and urethane pad, adhere to the glass, and cause fogging were analyzed. As a result, the main causative substance is the reaction of amine component derived from urethane pad (triethylenediamine = DABCO, catalyst used for urethane pad production) and leather-derived sulfate ion (synthetic tannin is considered to be the main source). And a component derived from a greasing agent. Details are as follows.
(A) As a result of performing IR analysis and elemental analysis of the fogging cause substance, a peak that may be an amide or SO ₃ and a peak that may be a sulfone or sulfate ion moiety were detected by IR. Since S was detected by elemental analysis, it was presumed that the amine component (triethylenediamine = DABCO) derived from the urethane pad and the sulfate ion derived from leather reacted.
Triethylenediamine is an amine catalyst used in polyurethane production. From this, it has been pointed out that triethylenediamine reacts with a flame retardant and causes fogging (Japanese Patent Application Laid-Open No. 8-217846). It was considered that a large amount of sulfate ions were included in the natural leather to be tested.
(B) The sulfur component in the leather is present. When the amount of sulfur component in the chemicals applied to the leather was investigated, it was found that 10% sulfur was present in the synthetic tannin used. It was thought that synthetic tannin was the source of the causative substance.
(C) As a result of performing GC-MS analysis on components that are soluble in an organic solvent among fogging-causing substances, triethylenediamine (DABCO), halogen phosphate phosphate flame retardants, poly A siloxane foam stabilizer was detected. In addition, fatty acids, fatty acid esters, and higher alcohols were detected as components considered to be derived from natural leather. These are considered to be mainly derived from the greasing agent.
(3) Based on the above analysis results, the present inventors first performed a water washing in the re-tanning process in order to remove sulfate ions as a provisional countermeasure (a countermeasure within a range considered not to affect leather quality). Measures were taken to increase from 1 to 3 times and to use a degreasing agent (surfactant) for washing with water. Although a certain effect was recognized (reflectance 70% → 82%), there was a problem with one of the products after the countermeasures were taken, so measures such as raising the washing temperature further (40 ° C → 50 ° C) were added. However, the result was insufficient.
(4) In the retanning step, the tanning agent has been specified and selected. As a result, synthetic tanning and the like are preferred, and the current tanning agents are adopted. This is probably the best choice. As mentioned above, considering the situation when using a greasing agent in combination, it was only fully premised on synthetic tanning on the premise of preventing the occurrence of fogging, which has been sufficiently verified. It is not possible. Synthetic tanning has replaced the traditional plant tannins. Examining whether plant tannin is the result of plant tannin is as follows.
(5) Synthetic tannins, resin tanning agents and greasing agents were used as treatment agents used in a series of conventional retanning / dyeing / greasing steps, and no vegetable tannins were used. Plant tannin is one of the polyphenol compounds, and is known to have protein adsorption, metal ion chelation, antioxidant activity, and the like, and is also said to have lipid adsorption. By incorporating this into leather, it can be expected to adsorb fogging-causing substances and prevent free divergence. Therefore, since it was considered that the effect could be improved by using a composition containing plant tannins, a treatment for retanning / greasing process was examined.
In this case, in addition to suppressing fogging below a certain standard, the softness, softness and volume feeling required for natural leather base for automobile seats, good appearance, heat resistance, tensile strength, etc. It is necessary to achieve. From the experience of the present inventors in the production of natural leather and the knowledge about the fogging-causing substance, the following is predicted to be effective and will be demonstrated.
(A) The treatment agent in the series of retanning / dyeing / greasing steps includes synthetic tannin, resin tanning agent and greasing agent in addition to plant tannins. The process is a process of further imparting “leatherness” to the leather that has undergone the tanning process. "Leather-likeness" refers to flexibility (easiness of elongation, easiness of bending), soft touch (feel), volume (enhancement), etc., and is always required for natural leather for automobile seats.
In addition, it is an important role of the retanning / greasing process to suppress silver float (a phenomenon in which the appearance of the leather deteriorates due to peeling of the leather surface nipple layer and the net layer).
In addition to this, heat resistance and tensile strength are also required, and heat resistance is achieved by the tanning process, but the tensile strength is further improved by retanning, dyeing and fatting.
In order to achieve the above-mentioned role required for the retanning / dyeing / greasing step, it is necessary to use a combination of synthetic tannin, resin tanning agent and greasing agent in addition to plant tannin. Each role is described below.
Dyeing is the role of adjusting the color of the leather and is not related to the achievement of “leatherness” or tensile strength.
(B) Each drug has an appropriate amount to be used, specifically as follows. The amount of each tannin drug used is expressed as a percentage by weight of the shaving leather. Shaving leather is leather that has undergone a tanning process and has been subjected to shaving (the thickness is adjusted by scraping the flesh side) and contains about 50 to 60% of moisture.
(I) Plant tannins Plant tannins have the property of discoloring to yellow or the like when exposed to light. If the discoloration is significant, there is a problem in appearance, so the amount used is preferably 12% by weight or less. More preferably, it is 8 wt% or less.
(Ii) Synthetic tannin Although it is a drug having a function similar to that of plant tannin, it is used in combination with plant tannin because plant tannin alone has a limit in the amount of use and a sufficient effect cannot be obtained. The total amount with the plant tannin is 7 to 25% by weight. If it is less than this range, the effects required for retanning, such as flexibility, soft touch, volume, and tensile strength, are not sufficient. If it is too much, it becomes hard to touch.
(Iii) Resin tanning agent The resin tanning agent functions to suppress silver float and is used in an amount of 2 to 12% by weight. If it is less than this range, the suppression of silver floating is insufficient and there is a risk of appearance problems. If it exceeds this range, it becomes hard to feel.
(Iv) Greasing agent Greasing agents give leather a soft and soft feel. The amount used is 6 to 14% by weight. If it is less than this range, it becomes hard to feel. If the amount is too large, silver floating may occur, which may cause a problem in appearance.
(C) Relationship between the amount of plant tannin, synthetic tannin, and greasing agent used From the analysis results of fogging causative substances contained in the composite of natural leather and urethane pad, the main sources of causative substances are urethane pad, synthetic tannin and Since it was considered as a greasing agent, it is thought that plant tannin should be used according to these amounts. For natural leather itself, it should be sufficient to adsorb fogging agents and fogging-causing substances derived from synthetic tannins, but it is also necessary to leave room for adsorbing substances derived from urethane pads. It is. The idea of using up to 12% by weight of the plant tannin and making the synthetic tannin greasing agent below a certain level can also be used. Actually, since the performance required for natural leather products is not uniform, it is desirable to set as high a degree of freedom as possible. From the above consideration, as a result of intensive studies on the relationship between the amount of plant tannin, synthetic tannin and the amount of greasing agent used (% by weight relative to shaving leather), the reflectance is 80% or more when the following relationship is established between them. As a result, an empirical rule was found and the present invention was achieved.
Greasing agent + synthetic tannin-plant tannin ≦ 22.0
The above conditions are applicable to the natural leather excluding the urethane pad, which is one of the sources of fogging, because the above conditions are applicable to the composite of natural leather and urethane pad.
(5) The present invention is as follows, including the natural leather for automobile seats subjected to the finishing process.
(A) The following specific proportions of the composition are employed in a series of steps of retanning, dyeing and greasing of natural leather production. 2 to 12% by weight of vegetable tannin, 7 to 25% by weight of synthetic tannin and 2 to 12% by weight of resin tanning agent, and 6 to 14% by weight of shaving leather Good results can be obtained if the composition contains 1% greasing agent and the content (% by weight) of plant tannin, synthetic tannin and greasing agent is in the relationship of formula (I).
Formula (I) Synthetic tannin + greasing agent-plant tannin ≤ 22.0
(B) A pre-treatment step before tanning, a tanning step, a shaving step, a re-tanning / dyeing / greasing step, and a drying step, and then a base coat layer, a color coat layer and a top coat layer are formed. In the method for producing natural leather, the method for producing natural leather, wherein the composition (a) is used in the retanning, dyeing and greasing steps.
(C) Natural leather for automobile seats produced by the production method of (b) above.
(D) A composite of a natural leather for automobile seats and a urethane pad, wherein the natural leather for automobile seats of (c) above is attached to a urethane pad.

ADVANTAGE OF THE INVENTION According to this invention, the natural leather for motor vehicle seats suppressed to the generation | occurrence | production amount of fogging below a fixed level also on high temperature conditions can be obtained.
In addition, according to the present invention, it is possible to obtain a natural leather for automobile seats that suppresses the occurrence of fogging below a certain level even under a high temperature condition even for a composite in which the natural leather for automobile seats is attached to a urethane pad. it can.

The natural leather of the present invention is prepared using an animal, for example, bovine raw hide, a preparation process, a tanning process, a water squeezing process, a shaving process, a retanning / dyeing / greasing process, a setter process, a drying process, a vibration process, and a buffing process. In the re-tanning / dyeing / greasing process, the use of a processing agent containing vegetable tannin, synthetic tannin, resin tanning agent and greasing agent is a manufacturing feature. Hereinafter, each step will be described. In addition, the general method for producing natural leather is detailed in the new edition leather science (Japan Leather Technology Association).

The preparation process for manufacturing leather is an already well-known process. In the pickling / lime picking process, the raw skin peeled off at the slaughterhouse is preserved in a salted state (raw skin), put into a drum, and salt and filth are washed away with water to return to the raw skin state. Perform hair removal using alkaline chemicals. Sodium sulfide or sodium hydrosulfide may be used as a hair loss promoter. In the refreshing process, surplus materials (back nibs) such as fat adhering to the back side of the skin obtained in the above-mentioned soaking / lime picking process are mechanically removed. In the band knife process, the skin is roughened to a thickness determined according to the purpose using a band machine and divided into a silver layer and a floor skin. The silver layer is a layer on the body surface side, is dense and smooth, and is an excellent material. The floor skin is a layer of internal leather, and the fibers are rough and poor in smoothness. However, a good quality leather can be obtained by devising the subsequent processing.

Next, in the tanning process, the skin is tanned with a tanning agent in a tanning drum, thereby cross-linking the collagen material of the skin to give the skin heat resistance, resistance to microorganisms and chemicals, and give flexibility. . Through this process, “skin” becomes “leather”.
A widely used tanning agent is a chromium compound using a trivalent chromium complex, for example, hexaacocrystalline sulfuric acid expressed as Cr ₂ (SO ₄ ) ₃ . Leather tanned with a chrome tanning agent is called wet blue because it is colored blue. It is also possible to purchase wet blue and wet white instead of carrying out the entire leather manufacturing process at one factory, and to start manufacturing after the tanning process.
As described above, there are many types of tanning agents, all of which are conventionally known, and commercially available products may be purchased and used.

In the water squeezing step, the tanned leather is squeezed with a water squeezing machine to keep the moisture contained in the leather constant.

In the shaving process, the tanned wet leather is shaved to a certain thickness with a shaving machine according to the target product thickness. The moisture of the leather after shaving is about 50-60% by weight, and there is relatively little fluctuation.

Retanning, dyeing, and greasing are processes that have different roles, but the chemicals are added one after another without affecting each other and draining the processing liquid in the drum through these operations. This process is collectively called retanning, dyeing, and greasing. The amount of the chemical used in the retanning / dyeing / greasing step is determined by a weight ratio with respect to the weight of the leather after shaving (including shaving leather and moisture of 50 to 60% by weight).
The total weight of the treatment agent including water in the chemical is about 1 to 3 times the weight of the shaving leather.
Retanning involves tanning with a different type of tanning agent than the tanning process, and does not only mean the reinforcement of tanning, but also imparts new characteristics to leather in order to increase added value. Improves the suitability of buffing and embossing by reducing the elasticity of the fiber (plant tannin), promotes separation of the fiber bundle into individual fibers, increases the fiber voids, and gives a feeling of fullness of the leather (solidity) (plant tannin, synthesis Tannin), improvement of the tightness of the silver surface (prevention of silver float), leather with a sense of volume by depositing a retanning agent between fibers of a relatively loose and low density tissue such as leather abdomen (Plant tannin, synthetic tannin, resin tanning agent) and the like.

The present inventor has found for the first time that plant tannin has a fogging-inhibiting effect that has not been known so far. It has been found that it is effective when used as a composition containing plant tannin as a retanning agent. Plant tannin is a kind of polyphenol compound contained in plants, and there are mimosa, cod, chestnut, quebracho, milobaran and the like as a kind used as a retanning agent. The following properties are relevant to reproduction.
(A) It is weak anionic.
(B) Since there are many carboxyl groups, hydroxyl groups, aromatic rings and the like in the molecule, the ability of nonionic binding intermolecular interaction is high. For this reason, plant tannin molecules are more or less assembled, form a polydisperse with a colloidal character with a wide particle size distribution, and have a strong adsorption activity. In particular, it has strong reactivity with cationic substances and is widely used as a retanning agent for chrome leather.
(C) The particle size and reactivity of plant tannins are influenced by the concentration and temperature, and are promoted or suppressed by the presence of electrolytes, sugars, low-molecular polar substances, and the like.
(D) The chemical stability of plant tannins is said to be slightly inferior.
The mechanism by which plant tannin suppresses fogging is not well understood, but the amino group of the amine component derived from urethane pad (triethylenediamine = DABCO, catalyst used for urethane pad production), which has the greatest influence on fogging, is plant tannin. There is a possibility that it is ionically bonded to a phenolic hydroxyl group contained in a large amount and the volatilization of triethylenediamine is suppressed. Further, it is considered that the greasing agent may be adsorbed to suppress volatilization and may be decomposed by antioxidant action.
Plant tannins are commercially available in powder form and can be purchased and used. The kind of plant tannin is not particularly limited.

On the other hand, the disadvantages of plant tannins are low light resistance and easy yellowing due to light. When the amount of plant tannin used is too large, yellowing becomes remarkable. Considering the above points, it can be seen that it is difficult to obtain a retanning effect using only plant tannin as a retanning agent.
Therefore, it is desirable to perform retanning in combination with synthetic tannin and a resin tanning agent. In addition, since the effects of plant tannins, synthetic tannins, and resin tanning agents are different, using them in combination makes it possible to obtain a well-balanced leather such as texture and texture.

Synthetic tannin is an aromatic synthetic tannin agent. A compound obtained by condensing a sulfonated aromatic compound alone or together with other usually unsulfonated aromatic compounds with formaldehyde and / or urea. Examples of suitable aromatic compounds for this purpose are naphthalene, biphenyl, terphenyl, phenol, cresol, 4,4′-dihydroxydiphenylsulfone, β-naphthol, dihydroxybenzene, resorcinol, 2,2-bis ( Hydroxyphenyl) propane, and diaryl ethers such as diphenyl ether and ditolyl ether, which may be sulfonated in a manner known per se. Aromatic synthetic tannins are the following compounds: (I) condensation product of sulfonated phenol or cresol and formaldehyde, (II) condensation product of naphthalene sulfonic acid and formaldehyde, (III) aryl sulfonic acid Or a formaldehyde condensation product of 4,4′-dihydroxydiphenylsulfone with (hydroxy) arylsulfonic acid added, (IV) a formaldehyde condensation product of a sulfo-containing aromatic hydroxy compound with aralkyl halide added, (V ) Phenol and phenol sulfonic acid urea-formaldehyde condensation product, (VI) Phenol and sulfonating agent reaction product, wherein the molar ratio of phenol: SO ₃ is (1) :( 1.1 to 2.2 (VII) sulfonated diaryl ester Condensation products of ter and formaldehyde, (VIII) sulfonated-biphenyl or -Condensation products of terphenyl and formaldehyde, (IX) 4,4'-dihydroxyphenyl sulfone and sulfonated 4,4'-dihydroxyphenyl A condensation product of sulfone and formaldehyde. (X) Formaldehyde condensation product of diaryl ether sulfonic acid and 4,4′-dihydroxydiphenyl sulfone; (XI) Formaldehyde condensation product of phenol with addition of aryl sulfonic acid or hydroxyaryl sulfonic acid.
The properties of synthetic tannin are as follows.
a) It is strongly anionic and has a remarkable effect of decreasing the positive charge of chrome leather and increasing the negative charge.
b) It has high reactivity with cationic substances such as chrome leather and is adsorbed mainly by ionic bonds.
c) The composition is generally complex and a multi-component mixture.
e) Chemical stability is slightly inferior and easily oxidized.
Synthetic tannin contains about 10% of sulfur and may be a fogging cause substance derived from leather. In order to suppress fogging, it is desirable to reduce the amount used as much as possible.
As for the synthetic tannin, a commercially available product may be purchased and used. As a product that can be used in the present invention, Basintan DLX-N, Basintan MLB, Basintan SW, Tamol NA (manufactured by BASF), Ucatan GM, Ucatan INF, Ucatan SWL (manufactured by Schill + Seilacher), Tanigan OS, Tanigan 3LN, Tanigan BN, Tanigan F, Tanigan ZF (hereinafter Lanxess) and the like.

There are the following types of resin tanning agents.
(I) Condensates of amino compounds such as urea, dicyandiamide, and melamine with formaldehyde, and (II) polycondensates that do not use formaldehyde (acrylic acid, isocyanate polymers, etc.).
In the type (I), there is a type in which the condensation reaction with formaldehyde is kept light, and the leather is infiltrated into leather in a relatively low molecular weight form and then polymerized by condensation. Since more or less residual methylol groups are present, condensation may proceed in the leather. Some are strongly anionic due to the introduction of a sulfone group, and others are cationic.
The type (II) is much higher in molecular weight than (I) and is usually in the form of a viscous solution or emulsion. Because it is a relatively coarse particle, it does not penetrate into the dense structure of leather, but concentrates on the loose parts of the tissue, such as the berry, to increase the filling effect and homogenize the leather structure. Use for purposes. It has the effect of suppressing silver float.
As the resin tanning agent, a commercially available product may be purchased and used as a product that can be used in the present invention. (Manufactured by BASF), Delgan NG (made by Schill + Seilacher), and the like.

Dyeing process The dyeing process is a process of coloring leather with a dye. The color of the leather surface depends on the color of the pigment in the coating layer, but it looks natural when looking at the cross section of the leather by bringing the color inside the leather as close to the color of the coating layer as possible.
As dyes, acid dyes and direct dyes (so-called anionic dyes) are often used, and most are azo dyes. Other examples include basic dyes and sulfur dyes. These dyes can be used by purchasing commercially available products.

Greasing process Chrome leather, which covers the main field of leather products, requires more or less flexibility.
It is not enough to mechanically dry the leather. It is necessary to apply an appropriate oil called a greasing agent. When the tanned leather is wet with water, the flexibility of the fiber is maintained due to the water present in the fiber bundle and in the fiber gap. When dried, the fibers stick together and the fibers and tissue harden.
If an oil agent, which is a substance that inhibits adhesion between fibers, is present in advance before drying, the tissue does not harden even if dried. This is because the water in the leather fiber is replaced by the oil agent. Furthermore, when an oil film is present between the fibers after drying or on the fiber surface, slippage between the fibers is improved and the leather is given flexibility. The purpose of greasing is to expect the inter-fiber lubrication effect first. In addition, it affects the protection of leather fibers such as water repellency and waterproofness, and the feel, bulge and gloss of leather.

The greasing agents include the following. These are selected and used.
(1) Anionic greasing agents are as follows.
(A) Sulfated oil Sulfated oil is a product obtained by adding sulfuric acid to natural unsaturated fats and oils to form a sulfate ester. A part of hydroxyl groups and double bonds are sulfated.
Sulfated fatty acid ester: Lipoder Liquor PU (manufactured by BASF),
Synthetic sulfonated lipid: SYNCUROL KV (manufactured by MUNZING),
Mixture of sulfonated ester and hydrocarbon: SYNCUROL 79 (manufactured by MUNZING), sulfonated ester: SYNCUROL SE (manufactured by MUNZING)
Synthetic sulfonated esters: SYNCUROL PF, MAX (manufactured by MUNZING) etc.
(B) Sulfonated oil The sulfonated oil is obtained by treating a synthetic oil natural oil having an unsaturated group with sulfuric anhydride, fuming sulfuric acid, chlorophonic acid or the like, and sulfonating the double bond in the molecule for neutralization.
Examples of the sulfonated oil include SK oil HF (manufactured by Sampras), Perastol ES (manufactured by Zschimmer & Schwarzchemisfabriken) and the like.
SK oil HF is a synthetic sulfonated oil having yellowing resistance, and is a mixture of 50% by weight of unreacted raw oil, 25% by weight of its sulfate ester and 25% by weight of the hydrolysis product.
Other examples include Turcon FA-200 (manufactured by Taiko Yushi Chemical Co., Ltd.), Pergrasol SF (manufactured by Zschimmer & Schwarzchemisfabriken). Turcon FA200 is a mixture of fatty acid monoglyceride, sulfonated natural oil, oxidation products thereof, and the like.
(C) Sulphite oil Sulphite oil is a sulfonate salt obtained by using a highly unsaturated natural oil or synthetic oil as a raw material and using sulfite as a sulfonating agent.
Mixture of sulfitized fish oil, natural oil and emulsifier: Lipsol EB (manufactured by MUNZING), sulfitized fish oil: OPTIMALIN UPNC (manufactured by MUNZING), vegetable oil, water-soluble emulsion of sulfitized animal oil: Lipoder Liquid A1 (manufactured by BASF),
(D) fatty acid soap,
Fatty acid soap is a soap obtained by saponifying natural fats and oils with an alkaline aqueous solution. Ammonium salts and potassium salts are also used as greasing agents. Since fatty acids are liberated on the acidic side from neutral, there are effects of surfactant components and neutral oil.
Modified fatty acid: Lipoder Liquor LA (manufactured by BASF)
(E) Phospholipids such as phosphorylated oil yolk and soybean lecithin have been used. Recently, phosphorylated oils are often used in higher alcohols or phosphate esters of polyoxyethylene alkyl ethers.
Emulsion of a mixture of synthetic oil and lecithin oil: Lipsol LQ (manufactured by Schill + Seilacher)
Phosphate oil: Lipoder Liquor PU (manufactured by BASF)
Formulation of sulfated vegetable oil, fatty alcohol phosphate ester and hydrocarbon: Ricker KIM
(Nagi Shokai)
(F) Multipolar greasing agents are a mixture of anionic, non-ionic and small amounts of cationic greasing agents.
(G) Other anionic greasing agents include mono- or dialkyl succinic acid, alkyl malonic acid, those having complex active groups such as carboxylate at both ends of the alkyl chain, and polyacrylic acid derivatives having long chain alkyl groups.

Cationic greasing agents Cationic greasing agents include quaternary ammonium salts, aliphatic amines, and aliphatic polyamine condensates.
Amphoteric greasing agents For amphoteric greasing agents, lecithin has long been used as a greasing agent having both anionic and cationic properties within the same molecule.
Nonionic greasing agents Nonionic greasing agents are rarely used alone and are used in combination with anionic and cationic greasing agents.
Aqueous solution of natural oil and nonionic surfactant: Lipoder Liquor IC (manufactured by BASF), mixed aqueous solution of wax and natural oil and surfactant: Lipoder Liquor SC (manufactured by BASF),
Aqueous solution of nonionic surfactant, sulfite oil and sodium salt: Lipoder Liquid WF (manufactured by BASF), mixture of natural oil, synthetic oil and synthetic emulsifier: Lipsol MSG (manufactured by MUNZING)
-Neutral oils, specifically (i) animal oils, (b) marine animal oils, (c) vegetable oils, (d) mineral oils, and (e) synthetic oils.
Used in combination with a greasing agent.

The retanning / dyeing / greasing process is performed as follows using a retanning drum.
Wash the leather after shaving and drain. Next, about twice the weight of the leather is put into the retanning drum. In the case of chrome-tanned leather, the pH is as low as 3-4, so it is neutralized with sodium hydrogen carbonate or sodium formate to about 4.5-6.0.
The vegetable tannin, synthetic tannin and resin tanning agent are added and the drum is turned to treat the leather. The order of input is not particularly limited.
The dye is then charged and the drum is turned to treat the leather.
The greasing agent is then added and the drum is turned to treat the leather.
Next, the pH of the treatment solution is lowered to about 3.5 to 4.0 with formic acid to fix the dye.
The greasing agent does not necessarily need to be added at once, and may be added in several times.
Finally, the treatment liquid is drained, the leather is washed with water, and the retanning / dyeing / greasing process is completed.

In the setter process, the moisture contained in the leather is squeezed out by the setter, and the leather is stretched to facilitate drying in the next process. The moisture of the leather after the setter process is about 50 to 60% of the leather weight.

Drying includes dry drying, vacuum drying, netting drying, etc., which can be used depending on the application. Sometimes combined. Garage drying is a method of drying leather by sending hot air from the opposite direction of movement while moving the suspended leather. In vacuum drying, drying time is shortened by drying under low pressure. Net tension drying is a technique of drying leather with a toggle between leather and net, and has the effect of suppressing the shrinkage of the leather.

The vibration process is a process in which the leather to which the fibers have been fixed after drying is given an appropriate moisture to be matured (taste removal), and vibration is applied with a vibrator to loosen the fibers. Further, there is a case in which softening is achieved by putting leather in an empty drum and turning it, and knocking it by dropping it in the leather drum.

In the buffing process, dirt and scratches on the surface of the silver surface are scraped off with sandpaper using a buffing machine, and the leather surface is made smooth and uniform.

The finish painting step is a step of forming a coating layer consisting of three layers of a base coat, a color coat and a top coat on the surface of the leather. In some cases, embossing (giving various uneven patterns by embossing) may be performed after base coat formation or color coat formation. In the base coat, the paint film and leather are closely adhered and colored with a pigment. The color coat is finally adjusted (toned) to the product color to obtain a uniform surface color. The top coat consists of a top coat that imparts surface properties such as gloss, adjustment, wear resistance, and touch.
These coating layers play an important role in obtaining the abrasion resistance, good tactile sensation, and moderate gloss required for natural leather for automobile seats, but do not cause fogging. These components can be freely determined within a range that satisfies the physical properties required for natural leather for automobile seats.

(1) Formation of base coat layer It is a layer for preparing for forming the layer stably on the upper surface, which is formed in front of the color coat layer and the top coat layer, flattening irregularities on the leather surface. It also has a function to stably and securely couple the two. In forming this layer, a composition comprising a resin, a crosslinking agent, a pigment and water is applied to the surface of the floor leather. The total solid content is adjusted to 30 to 40% by weight with water.
As the resin, a two-component polyurethane resin, an acrylic / urethane resin, or an acrylic resin is used. Isocyanate etc. are used for a crosslinking agent. A pigment of a color to be colored is used as the pigment. The solid content weight ratio of the resin, the crosslinking agent, and the pigment is 88 to 92: 2 to 8: 3 to 9 (100 in total). In addition, auxiliary agents such as thickeners and leveling agents may be added.
As the coating method, brush coating, spraying, curtain coating, and roll coating are appropriately selected and used in a state containing an aqueous solution. The coating amount is 55 to 100 g / m ² , and after application, warm air is applied to the surface to dry. The film thickness is 10-20 μm.
After the application, warm air is applied to the surface and dried.

(2) Formation of color coat layer The color coat layer is a layer for allowing pigments and dyes for coloring leather to be present, and is provided on the upper part of the base coat as viewed from the floor leather. In forming this layer, a composition comprising a resin, a crosslinking agent, a filler agent, a pigment, an auxiliary agent and water is applied to the surface of the base coat.
As the resin, a two-component polyurethane resin, a two-component polyurethane / acrylic resin, or an acrylic resin is used. Isocyanate etc. are used for a crosslinking agent. A pigment of a color to be colored is used as the pigment. Auxiliaries include leveling agents, thickeners, light fasteners, foam stabilizers and the like. The total solid content is adjusted to 30 to 40% by weight with water.
The solid content weight ratio of the resin, the crosslinking agent, the filler agent, the pigment and the auxiliary agent is 50 to 70: 5 to 15: 4 to 10:15 to 25: 3 to 7 (100 in total). As a coating method, spray, curtain coating, and roll coating are appropriately selected and used in a state containing an aqueous solution. The coating amount is 45 to 70 g / m ² , and the coating is dried by applying warm air to the surface after coating. The film thickness is 10-15 μm.

Formation of Top Coat Layer The top coat layer is formed on the surface of the color coat layer and imparts wear resistance by making the coating film surface strong and hard. At the same time, a tactile sensation agent is added to improve the feeling of sliminess and squeak, and a matting agent (matting agent) is added to prevent unnatural shine. In some cases, a resin preparation containing polyurethane fine particles or the like is used for matting. In forming this layer, a composition comprising a resin, a crosslinking agent, a matting agent, a tactile agent, an auxiliary agent and water is applied to the surface of the color coat. The total solid content is adjusted to 30 to 40% by weight with water.
As the resin, a two-component polyurethane resin, a two-component polyurethane / acrylic resin, or an acrylic resin is used. Isocyanate etc. are used for a crosslinking agent. Silica fine particles or the like are used as the matting agent. As the touch agent, a silicone-based touch agent, wax or the like is used. Auxiliaries include leveling agents, thickeners and the like.
The solid content weight ratio of the resin, the crosslinking agent, the matting agent, and the leveling agent is 55 to 65:15 to 30: 0 to 15:10 to 20: 2 to 7 (total 100). As a coating method, spray, curtain coating, and roll coating are appropriately selected and used in a state containing an aqueous solution. The coating amount is 30 to 45 g / m ² , and the coating is dried by applying warm air to the surface.
The coating amount is 60 to 90 g / m ² . In some cases, the coating is applied in two steps, in which case the drying process is performed between the first and second coatings. The film thickness is 5 to 15 μm.

Evaluation method of fogging performance (1) Aggregation of volatile matter on glass plate A windscreen fogging tester WF-2 (manufactured by Suga Test Instruments Co., Ltd.) was used. In a cylindrical beaker (diameter 90 mm, height 190 mm), put a urethane pad 80 mm in diameter x 40 mm in height and leather 80 mm in diameter with the leather facing up, and use a glass plate (110 x 110 x 3 mm) The cap was put in an oil bath kept at 100 ° C. and heated for 72 hours. The glass plate was cooled by applying a cooling device set to 20 ° C. from above.
(2) Reflectance measurement of glass plate The reflectivity of the glass plate obtained by agglomerating the volatiles obtained in (1) above was measured using a gloss measuring device REFO60 (manufactured by HACH LANGGE, Germany).
(3) Setting of reference value If the measurement result of the reflectance by the reflectance measuring device of the glass plate is 80% or more, it can be said that fogging does not occur in the actual vehicle (it does not cause a problem even if it occurs). ).

(1) Using cattle salted hide, preparation process, tanning process, water squeezing process, shaving process, re-tanning / dyeing / greasing process, setter process, drying process, vibration process, buffing process, finishing coating process Natural leather was produced. Tanning was performed using a chromium tanning agent.
(2) The composition used in a series of steps of retanning, dyeing and greasing is as follows. The amount used was expressed as a percentage by weight relative to the shaving leather. Plant tannin (mixture of mimosa and cod) 2.0% by weight, synthetic tannin 6.0% by weight, resin tanning agent 10.0% by weight, greasing agent (mixture of oil and mineral oil) 9.0% by weight. In addition to this, a dye was added.
The relationship between the use amounts (% by weight) of synthetic tannins, greasing agents and vegetable tannins is as follows.
Synthetic tannin + greasing agent-plant tannin = 13.0
(3) The solid content composition of the paint used in the finishing step is as follows. The total solid content is adjusted with water so as to be 35%.
Base coat two-component urethane resin 40% by weight, acrylic resin 48% by weight, cross-linking agent (isocyanate) 6% by weight, pigment 6% by weight.
60% by weight of a color coat two-component urethane resin, 10% by weight of a crosslinking agent (isocyanate), 7% by weight of a filler agent, 19% by weight of a pigment, and 5% by weight of an auxiliary agent (leveling agent and light fastness agent). The solid content composition of the paint is as follows. The total solid content is adjusted with water so as to be 35%.
59% by weight of top coat two-component urethane resin (including preparations containing polyurethane fine particles), 23% by weight of cross-linking agent (isocyanate), 14% by weight of touch agent (silicone tactile agent, wax), auxiliary agent (leveling agent, increase) Viscosity) 4% by weight.
(4) The fogging performance of the natural leather obtained above was evaluated by the reflectance of the glass plate in a state where the urethane pad was superimposed on the natural leather back surface by the above-described method.
As a result of evaluating the reflectance of the glass plate with respect to the fogging performance of the treatment agent used in the retanning / dyeing / greasing process, the reflectance was 82.0%, which was 80.0% as a reference value. .

Natural leather was produced in the same manner as in Example except that the amount of plant tannin used was 4.0% by weight, and the fogging performance was evaluated. . The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 11.0
Reflectance of glass plate: 87.0%

Composition used in a series of steps of re-tanning / dyeing / greasing process: 5.0% by weight of vegetable tannin, 2.0% by weight of synthetic tannin, 2.0% by weight of resin tanning agent, greasing agent A natural leather was produced in the same manner as in Example 1 except that 7.0% by weight was used, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 4.0
Reflectance of glass plate: 92.0%

Composition used in a series of steps of re-tanning / dyeing / greasing process: 6.0% by weight of vegetable tannin, 4.0% by weight of synthetic tannin, 2.0% by weight of resin tanning agent, greasing agent A natural leather was produced in the same manner as in Example 1 except that the content was changed to 6.0% by weight, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 4.0
Reflectance of glass plate: 95.9%

Natural leather was produced in the same manner as in Example 1 except that the plant tannin was changed to 6.0% by weight, and fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 9.0
Reflectance of glass plate: 95.0%

Example of composition used in a series of retanning / dyeing / greasing steps, except that vegetable tannin was 6.0 wt%, synthetic tannin was 10 wt%, and resin tanning agent was 11.0 wt%. Natural leather was produced in the same manner as in No. 1 and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 13.0
Reflectance of glass plate: 83.6%

Composition used in a series of retanning, dyeing and greasing steps is 8.0% by weight of vegetable tannin, 12.5% by weight of synthetic tannin, 12.0% by weight of resin tanning agent, and greasing agent A natural leather was produced in the same manner as in Example 1 except that the content was changed to 14.0% by weight, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 18.5
Reflectance of glass plate: 84.3%

Reference example 1

The plant tannin used in the series of retanning, dyeing and greasing steps is 8.0 wt%, synthetic tannin is 16.8 wt%, resin tanning agent is 12.0 wt%, and greasing agent is 14.0 wt%. Except for the weight percentage, natural leather was produced in the same manner as in Example 1, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 22.8
Reflectance of glass plate: 84.3%

Comparative Example 1

Natural as in Example 1 except that plant tannin is not used in the retanning / dyeing / greasing process, the amount of resin tanning agent used is 3.5% by weight, and the amount of greasing agent used is 6.5% by weight. Leather was manufactured and fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 12.5
Reflectance of glass plate: 72.0%

Comparative Example 2

Plant tannin is not used in re-tanning / dyeing / greasing process, synthetic tannin usage is 6.3% by weight, resin tanning agent usage is 5.0% by weight, and greasing agent usage is 6.5% by weight. Except that, natural leather was produced in the same manner as in Example 1, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 12.8
Reflectance of glass plate: 72.0%

Comparative Example 3

Plant tannin is not used in the retanning / dyeing / greasing process, the amount of synthetic tannin used is 12.5% by weight, the amount of resin tanning agent used is 13.0% by weight, and the amount of greasing agent used is 14.0% by weight. Except that, natural leather was produced in the same manner as in Example 1, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 26.5
Reflectance of glass plate: 61.3%

Comparative Example 4

No plant tannin is used in the retanning / dyeing / greasing process, the synthetic tannin consumption is 16.8% by weight, the resin tanning agent usage is 12.0% by weight, and the greasing agent usage is 14.0% by weight. Except that, natural leather was produced in the same manner as in Example 1, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 30.8
Reflectance of glass plate: 61.3%

Comparative Example 5

4.0% by weight of vegetable tannin, 12.5% by weight of synthetic tannin, 13.0% by weight of resin tanning agent, 14.0% by weight of greasing agent used in the retanning / dyeing / greasing process Except that, natural leather was produced in the same manner as in Example 1, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 22.5
Reflectance of glass plate: 78.0%

Comparative Example 6

4.0% by weight of vegetable tannin, 16.8% by weight of synthetic tannin, 12.0% by weight of resin tanning agent, and 14.0% by weight of greasing agent used in the retanning / dyeing / greasing process Except that, natural leather was produced in the same manner as in Example 1, and the fogging performance was evaluated. The relationship between the amounts of plant tannin, synthetic tannin and greasing agent used, and the results of fogging evaluation were as follows.
Synthetic tannin + greasing agent-plant tannin = 26.8
Reflectance of glass plate: 78.0%

The experimental results are summarized in Table 1.

The glass plate reflectance was found to decrease with an increase in the amount of use of the greasing agent and synthetic tannin, and to increase with an increase in the amount of use of the plant tannin.
When plant tannin was not used, the reference value of 80% of the glass plate reflectance could not be achieved. In addition, when plant tannin was used, when (synthetic tannin + greasing agent-plant tannin) was 22.0 or less, the glass plate reflectance standard value was all achieved, but it exceeded 22.0 There were cases where it could not be achieved.
In addition, about the natural leather of Examples 1 to 7 and Reference Example 1, as a result of testing for flexibility, abrasion resistance, fir resistance, tactile sensation, and light resistance, it reached a level that can be satisfactorily used as natural leather for automobile seats. It was.

Claims (4)

A composition used in a series of steps of retanning, dyeing, and greasing in the production process of natural leather, and 2 to 12% by weight of plant tannin, total of synthetic tannin and plant tannin based on the weight of shaving leather Containing 7 to 25% by weight of synthetic tannin, 2 to 12% by weight of resin tanning agent and 6 to 14% by weight of fatliquor, and the content of plant tannin, synthetic tannin and fatliquor (wt% ) Is in the relationship of formula (I).
Formula (I) Synthetic tannin + greasing agent-plant tannin ≤ 22.0 Natural leather that forms a coating consisting of a base coat layer, a color coat layer, and a top coat layer after passing through a pretreatment process before tanning, a tanning process, a shaving process, a retanning / dyeing / greasing process, and a drying process. In the manufacturing method, the composition of Claim 1 is used in a series of processes from a re-tanning, dyeing | staining, and greasing process, The manufacturing method of the natural leather characterized by the above-mentioned. A natural leather for automobile seats produced by the production method according to claim 2. A composite of natural leather for automobile seats and urethane pad, wherein the leather for automobile seats according to claim 3 is attached to a urethane pad.