JP4114371B2 - Thermosetting polyurethane elastomer molded article, method for producing the same, and composition used therefor - Google Patents

Description

【００４８】
【表２】

【００４９】
【表３】

【００５０】
【表４】

【００５１】
【発明の効果】
圧縮永久歪みが低く、低硬度であり、かつ成形性に優れた熱硬化性ポリウレタンエラストマー成形品が得られる効果を有する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermosetting polyurethane elastomer molded article, a method for producing the same, and a two-component curable composition.
[0002]
[Prior art]
Thermosetting polyurethane elastomers are excellent in wear resistance, mechanical properties, solvent resistance, and oil resistance. Therefore, industrial parts such as rolls and casters, automobile parts such as solid tires and belts, paper feed rolls, and copiers. In addition to OA equipment parts such as industrial rolls, it is widely used in sports and leisure goods.
[0003]
[Problems to be solved by the invention]
However, a conventional general thermosetting polyurethane elastomer has a hardness of about 50 to 100 (hereinafter referred to as “JIS A hardness”) according to A type of a spring type hardness tester defined by JIS K 6301. In particular, for applications that require flexibility, an elastomer having a lower hardness is required.
[0004]
As a method for obtaining a low-hardness thermosetting polyurethane elastomer, a method of adding a large amount of a plasticizer has been proposed, but there are problems of a decrease in strength, an increase in compressive strain, and surface stickiness due to bleed of the plasticizer. In addition, a method of reducing the crosslinking density using a raw material having a low number of functional groups has been proposed, but there are problems of a decrease in wear resistance and chemical resistance and a significant increase in compression set. Furthermore, a method for improving hardness and compression set by using diphenylmethane diisocyanate or carbodiimide-modified diphenylmethane diisocyanate, a high molecular weight polyol, and a polyfunctional curing agent was proposed (JP-A-8-151423). There was a problem that the viscosity of the product was high and molding defects were likely to occur.
[0005]
Therefore, there has been an increasing demand for a thermosetting polyurethane elastomer that can realize low hardness without increasing compression set and that has good moldability.
[0006]
[Means for Solving the Problems]
This invention is the following invention which solves the said subject.
Number average molecular weight 4000-12000, isocyanate group-terminated prepolymer (i) obtained by reacting polyoxyalkylene polyol (a) having an average hydroxyl number of 2-3 with tolylene diisocyanate, and number average molecular weight 4000-12000, Curing agent (ii) whose main component is polyoxyalkylene polyol (b) having an average number of hydroxyl groups of 2 to 3, wherein at least one of (a) and (b) has an average number of hydroxyl groups of more than 2. Is a thermosetting polyurethane elastomer molded product obtained by mixing and reacting,
A thermosetting polyurethane elastomer molded article having a compression set as defined by JIS K 6301 of 7% or less and a hardness by A type of a spring type hardness tester defined by JIS K6301 of 40 or less.
[0007]
Number average molecular weight 4000-12000, isocyanate group-terminated prepolymer (i) obtained by reacting polyoxyalkylene polyol (a) having an average hydroxyl number of 2-3 with tolylene diisocyanate, and number average molecular weight 4000-12000, Curing agent (ii) whose main component is polyoxyalkylene polyol (b) having an average number of hydroxyl groups of 2 to 3, wherein at least one of (a) and (b) has an average number of hydroxyl groups of more than 2. Is a method for producing a thermosetting polyurethane elastomer molded article,
A method for producing a thermosetting polyurethane elastomer molded article having a compression set defined by JIS K 6301 of 7% or less and a hardness of a spring-type hardness tester defined by JIS K 6301 according to type A of 40 or less.
[0008]
Number average molecular weight 4000-12000, isocyanate group-terminated prepolymer (i) obtained by reacting polyoxyalkylene polyol (a) having an average hydroxyl number of 2-3 with tolylene diisocyanate, and number average molecular weight 4000-12000, Curing agent (ii) whose main component is polyoxyalkylene polyol (b) having an average number of hydroxyl groups of 2 to 3, wherein at least one of (a) and (b) has an average number of hydroxyl groups of more than 2. A two-component curable composition comprising no low molecular plasticizer,
Two-part curing in which the obtained cured product has a compression set as defined by JIS K 6301 of 7% or less and a hardness by A type of a spring type hardness tester specified by JIS K 6301 Sex composition.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(Prepolymer)
In the present invention, tolylene diisocyanate is used as a raw material for the isocyanate group-terminated prepolymer. Examples of tolylene diisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, or a mixture thereof. 70 parts by mass of 2,4-tolylene diisocyanate in 100 parts by mass of all tolylene diisocyanates. What contains above is preferable.
[0010]
Tolylene diisocyanate and other polyisocyanate compounds may be used in combination, but the proportion of the other polyisocyanate compound is preferably 20 parts by mass or less, particularly preferably 10 parts by mass or less, and not used in combination. Is most preferred.
[0011]
In the present invention, a polyoxyalkylene polyol having a number average molecular weight of 4000 to 12000 and an average number of hydroxyl groups of 2 to 3 is used as a raw material for the isocyanate group-terminated prepolymer. A polyoxyalkylene polyol can be produced by reacting an alkylene oxide by a known method in the presence of an initiator.
[0012]
As the initiator, a compound having 2 to 8 active hydrogen atoms can be used. Specifically, a dihydric alcohol such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol; Trihydric alcohols such as methylolpropane, trimethylolethane, glycerin, 1,2,4-butanetriol, 1,2,6-hexanetriol; tetrahydric alcohols such as pentaerythritol and erythritol; 6 such as sorbitol and dipentaerythritol Octahydric alcohols such as tripentaerythritol and sucrose; diamines such as ethylenediamine, hexamethylenediamine and tolylenediamine; alkanolamines such as monoethanolamine, propanolamine and diethanolamine; bis Phenol phenol A and the like; and the like.
[0013]
These compounds can be mixed and used as an initiator so as to have a target average number of hydroxyl groups. The initiator is preferably a dihydric alcohol, a trihydric alcohol or a mixture thereof.
[0014]
Examples of the alkylene oxide include propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, and ethylene oxide. Propylene oxide or a combination of propylene oxide and another alkylene oxide is preferable. Only propylene oxide is preferable, and even when other alkylene oxide is used in combination, the proportion of propylene oxide is preferably 70% by mass or more.
[0015]
The molecular weight of the polyoxyalkylene polyol is 4000-12000. If the molecular weight is less than 4000, the molecular weight between crosslinks is low, so that the resulting molded article has high hardness. If the molecular weight exceeds 12,000, the crosslink molecular weight is high and compression set increases.
[0016]
The average number of hydroxyl groups of the polyoxyalkylene polyol is 2 to 3. An average number of hydroxyl groups of less than 2 is not preferable because the crosslink density decreases and compression set increases. On the other hand, if the average number of hydroxyl groups exceeds 3, the hardness increases due to an increase in the crosslinking density, the viscosity of the prepolymer increases remarkably, and the workability deteriorates. As will be described later, it is essential that at least one of the polyol of the isocyanate group-terminated prepolymer or the polyol contained in the curing agent exceeds 2.
[0017]
Further, the total unsaturation degree of the polyoxyalkylene polyol is preferably 0.07 or less, particularly 0.05 or less, and further preferably 0.03 or less. If the total degree of unsaturation exceeds 0.07, the crosslinking density decreases and compression set increases, which is not preferable. The total degree of unsaturation is represented by meq / g.
[0018]
The polyol may be a mixture of two or more. In that case, the number average molecular weight, the average number of hydroxyl groups, and the total unsaturation of the mixture may be in the above ranges.
[0019]
The isocyanate group-terminated prepolymer reacts tolylene diisocyanate with the above polyol at a ratio of isocyanate group / hydroxyl group (molar ratio) of 1.5 to 20, more preferably 1.8 to 15, and particularly 2.0 to 10. Can be manufactured. When the molar ratio is less than 1.5, the viscosity of the prepolymer is increased and workability is deteriorated. On the other hand, when the molar ratio is more than 20, foaming tends to be easily caused.
[0020]
The isocyanate group content (mass basis) of the prepolymer is preferably 0.6 to 8%, particularly preferably 0.8 to 6%, and more preferably 1 to 4%. If the isocyanate group content is less than 0.6%, the viscosity of the prepolymer is increased and workability is lowered. On the other hand, if the isocyanate group content exceeds 15%, foaming tends to occur, which is not preferable.
[0021]
The isocyanate group-terminated prepolymer can be produced by a known method. For example, it can be obtained by subjecting tolylene diisocyanate and the polyol to a heating reaction at 60 to 100 ° C. for 1 to 20 hours in a dry nitrogen stream.
[0022]
(Curing agent)
In the present invention, a curing agent mainly composed of a polyoxyalkylene polyol having a number average molecular weight of 4000 to 12000 and an average hydroxyl number of 2 to 3 is used as the curing agent. The polyoxyalkylene polyol can be the same as that used as a raw material for the isocyanate group-terminated prepolymer.
[0023]
The average number of hydroxyl groups is 2-3. If the average number of hydroxyl groups is less than 2, the crosslink density is lowered and the hardness is lowered, but the compression set is increased and the adhesiveness of the surface of the molded article is also increased. On the other hand, an average number of hydroxyl groups exceeding 3 is not preferable because the hardness increases due to an increase in the crosslinking density.
[0024]
As described above, it is necessary that at least one of the polyoxyalkylene polyol used for the isocyanate group-terminated prepolymer or the polyoxyalkylene polyol used for the curing agent has an average number of hydroxyl groups exceeding 2. In this invention, it is preferable that the average hydroxyl group number of the polyoxyalkylene polyol used for a hardening | curing agent exceeds 2, Preferably it is 2.2-3.0.
[0025]
The structure, average molecular weight, and total unsaturation of the polyoxyalkylene polyol are the same as those of the polyoxyalkylene polyol used as a raw material for the isocyanate group-terminated prepolymer. The polyoxyalkylene polyol used for the curing agent may be the same as or different from the polyoxyalkylene polyol used for the isocyanate group-terminated prepolymer.
[0026]
In the present invention, by using a specific polyoxyalkylene polyol as a curing agent, it has good miscibility with the isocyanate group-terminated prepolymer of the present invention. Because there is, workability is good.
[0027]
(Method for manufacturing thermosetting polyurethane elastomer molded product)
In the present invention, a thermosetting polyurethane elastomer molded article can be produced by reacting an isocyanate group-terminated prepolymer with a curing agent.
When the isocyanate group-terminated prepolymer and the curing agent are reacted, the molar ratio of isocyanate group / hydroxyl group is 0.9 to 1.2, preferably 0.95 to 1.15. . If it is less than 0.9, the compression set increases and the strength decreases remarkably. If it exceeds 1.2, there are problems such as increased hardness and foaming.
[0028]
Moreover, it is preferable that the usage-amount of the hardening | curing agent with respect to 100 mass parts of isocyanate group terminal prepolymer shall be 50-500 mass parts, and 50-350 mass parts is especially preferable. If the proportion of the curing agent is less than 50 parts by mass, a sufficient thinning effect of the prepolymer cannot be obtained, and if it exceeds 500 parts by mass, when mixed with the prepolymer, the dispersibility deteriorates and the homogenization does not occur sufficiently. There is a problem that tends to cause defects.
[0029]
It is preferable that the viscosity (25 degreeC) immediately after mixing the isocyanate group terminal prepolymer and hardening | curing agent of this invention is 20000 mPa * s or less. By setting it as such a viscosity range, workability | operativity becomes favorable and the problem of a molding defect does not arise easily. It is important to achieve such a viscosity range without blending a plasticizer. In the present invention, a plasticizer is not blended.
[0030]
A known urethanization reaction catalyst can be used when the isocyanate group-terminated prepolymer and the curing agent are reacted. For example, organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate and tin 2-ethylhexanoate; iron compounds such as iron acetylacetonate and ferric chloride; tertiary amines such as triethylamine and triethylenediamine Etc. Of these, organotin compounds are preferred.
[0031]
The addition amount of the catalyst is preferably 0.0001 to 0.1 parts by mass, particularly preferably 0.001 to 0.01 parts by mass with respect to 100 parts by mass in total of the prepolymer and the curing agent. If the amount is less than 0.0001 parts by mass, the time until the molded product can be removed becomes long. If the amount exceeds 0.1 parts by mass, the pot life after mixing the reaction components becomes too short.
[0032]
In this invention, you may mix | blend additives, such as a filler, a reinforcing agent, a stabilizer, a flame retardant, a mold release agent, an antifungal agent, with the said isocyanate group terminal prepolymer and hardening | curing agent as needed.
[0033]
Examples of fillers and reinforcing agents include carbon black, aluminum hydroxide, calcium carbonate, titanium oxide, silica, glass, bone meal, wood flour, fiber flakes, and examples of stabilizers include antioxidants and UV absorption. Examples of flame retardants include chloroalkyl phosphate, dimethylmethylphosphonate, ammonium polyphosphate, and organic bromine compounds. Examples of mold release agents include wax, soaps, and silicone oil. Examples of the antifungal agent include pentachlorophenol, pentachlorophenol laurate, and bis (tri-n-butyltin) oxide.
[0034]
In the present invention, the thermosetting soft polyurethane elastomer molded product can be molded using a mold after mixing the isocyanate group-terminated prepolymer and the curing agent. In this case, the temperature of the mold is preferably 60 to 150 ° C, particularly preferably 80 to 130 ° C. When the temperature is lower than 60 ° C, curing failure occurs and the curing time becomes longer. When the temperature is higher than 150 ° C, the reaction is too fast, and the composition hardens before spreading over the entire mold, or coloration occurs due to thermal deterioration. Neither is preferred. Moreover, the obtained molded article can complete a crosslinking reaction by heating at 60 to 100 ° C. for several hours as necessary after demolding (post-curing). In some cases, the remaining isocyanate groups can be eliminated by curing at room temperature for 1 to 3 days.
[0035]
As a method for casting into a mold, a reaction injection molding (RIM) method can be used in addition to various commonly used casting methods. Furthermore, the two-component curable composition of the present invention can be coated on various substrates by airless spray or the like and cured on the substrate to form a molded product.
[0036]
(Thermosetting polyurethane elastomer molded product)
The molded article thus obtained has a compression set specified by JIS K 6301 of 7% or less, and particularly preferably 3% or less. Moreover, the hardness by the A type | mold of the spring type hardness tester prescribed | regulated by JISK6301 is 40 or less, and 30 or less is preferable. That is, the thermosetting polyurethane elastomer molded article of the present invention can achieve a low hardness while maintaining a low compression set. In addition, it has an effect of excellent moldability.
[0037]
Therefore, as a use of the thermosetting polyurethane elastomer molded article of the present invention, it can be used for various rolls, vibration damping materials, impact absorbing materials and the like. It can also be used for applications such as sealing materials, potting materials, caulking materials, and coating materials.
[0038]
【Example】
Next, the present invention will be specifically described with reference to examples. “Part” indicates part by mass. Examples 1 to 3 are examples, and examples 4 to 5 are comparative examples.
[0039]
(Evaluation items and measurement method)
(1) Isocyanate group content (NCO group content): Measured according to JIS K 1603.
(2) Viscosity: Measured using an E-type viscometer EHD-R type (manufactured by Tokyo Keiki Co., Ltd.) at a measurement temperature of 25 ° C., a sample amount of 1.5 ml, and a standard rotor (1 ° 34 ′).
[0040]
(3) Hydroxyl value: Measured according to JIS K 1557.
(4) Compression set: According to JIS K 6301, a sample having a diameter of 29 mm and a thickness of 12.7 mm was compressed and fixed to 75% of the thickness, heated at 70 ° C. for 22 hours, and then at room temperature for 30 minutes. After leaving, the thickness was measured and calculated.
[0041]
(5) Surface hardness: According to JIS K 6301, a compression set sample (diameter 29 mm, thickness 12.7 mm) was measured using a type A spring type hardness tester.
(6) Tensile test: According to JIS K 6301, a dumbbell-shaped No. 3 test piece using a sheet having a thickness of 2 mm was measured in an atmosphere having a tensile speed of 50 mm / min, a temperature of 23 ° C., and a relative temperature of 65%.
[0042]
(7) Moldability: When 200 g was cast into a sheet mold (thickness 2 mm × 300 mm square) in a heating furnace maintained at 110 ° C. and cured by heating for 30 minutes, resin was present at the four corners of the mold. In addition, when the appearance of a molded product obtained by heating at 80 ° C. for 5 hours after demolding was observed and no bubbles were observed, and the hardness of the molded product was uniform, it was determined as “good”.
[0043]
(material)
As the polyols A1 to A5, polyoxypropylene polyols having properties shown in Table 1 manufactured using a zinc hexacyanocobaltate complex catalyst using the initiator shown in Table 1 were used. As isocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), diphenylmethane diisocyanate (MDI), carbodiimide-modified diphenylmethane diisocyanate (modified MDI) (Isocyanate group content 29%) was used.
[0044]
(Prepolymer production method)
The isocyanate shown in Table 2 was charged into a four-necked flask equipped with a stirrer, a dropping funnel, a nitrogen inlet tube and a thermometer, and the polyol shown in Table 2 was added while stirring under a dry nitrogen stream. An isocyanate group-terminated prepolymer was produced by maintaining the temperature in the flask at 90 ° C. for 5 hours. Table 2 shows the isocyanate group content and viscosity of the obtained prepolymer.
[0045]
(Method for producing curing agent)
The parts shown in Table 3 for the polyols shown in Table 3 and the parts shown in Table 3 for dibutyltin dilaurate (DBTDL) were mixed to produce a curing agent. Table 3 shows the average molecular weight, average hydroxyl value, average number of hydroxyl groups, and viscosity of the obtained curing agent.
[0046]
(Examples 1-3 and Comparative Examples 1-2)
The prepolymer and the curing agent of the combinations shown in Table 4 were each degassed under reduced pressure, and then mixed for about 3 minutes using a stirrer so as not to entrain bubbles, and the viscosity was measured (in the table, blended viscosity). This was poured into a mold for a compression set measurement sample and a mold for a tensile test measurement sheet in a heating furnace maintained at 110 ° C., heat-cured for 30 minutes, demolded, and further heated at 80 ° C. for 5 hours. Each molded product was obtained. The evaluation results of the physical properties and moldability are shown in Table 4.
[0047]
[Table 1]

[0048]
[Table 2]

[0049]
[Table 3]

[0050]
[Table 4]

[0051]
【The invention's effect】
This has the effect of obtaining a thermosetting polyurethane elastomer molded article having a low compression set, a low hardness and excellent moldability.

Claims (4)

Isocyanate group terminal obtained by reacting one or more polyoxyalkylene polyols (a) selected from polyoxyalkylene polyols having a number average molecular weight of 4000 to 12000 and an average hydroxyl number of 2 to 3 with tolylene diisocyanate. Number average molecular weight of 4000 to 12000 obtained by reacting a prepolymer and one or more alkylene oxides selected from propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide and ethylene oxide with an initiator , average Polyoxyalkylene polyol having 2 to 3 hydroxyl groups (b) [However, at least one of (a) and (b) has an average hydroxyl group number exceeding 2. A plasticizer-free thermosetting polyurethane elastomer molded product for various rolls, vibration isolator or shock absorber obtained by mixing and reacting,
The polyoxyalkylene polyol (a) and polyoxyalkylene polyol (b) used in the production of the prepolymer are prepared using a zinc hexacyanocobaltate complex catalyst, and the total unsaturation is 0.03 meq / g or less. And
A thermosetting polyurethane elastomer molded article having a compression set defined by JIS K 6301 of 7% or less and a hardness of A type of a spring type hardness tester specified by JIS K6301 of 40 or less. Isocyanate group terminal obtained by reacting one or more polyoxyalkylene polyols (a) selected from polyoxyalkylene polyols having a number average molecular weight of 4000 to 12000 and an average hydroxyl number of 2 to 3 with tolylene diisocyanate. Number average molecular weight of 4000 to 12000 obtained by reacting a prepolymer and one or more alkylene oxides selected from propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide and ethylene oxide with an initiator , average Polyoxyalkylene polyol having 2 to 3 hydroxyl groups (b) [However, at least one of (a) and (b) has an average hydroxyl group number exceeding 2. And a plasticizer-free thermosetting polyurethane elastomer molded article for various rolls, vibration isolator or shock absorber,
The polyoxyalkylene polyol (a) and polyoxyalkylene polyol (b) used in the production of the prepolymer are prepared using a zinc hexacyanocobaltate complex catalyst, and the total unsaturation is 0.03 meq / g or less. Use
A method for producing a thermosetting polyurethane elastomer molded article, wherein the compression set specified by JIS K 6301 is 7% or less, and the hardness of the spring type hardness tester specified by JIS K 6301 is 40 or less.   The manufacturing method of Claim 2 whose viscosity immediately after mixing the said prepolymer and the said hardening | curing agent is 20000 mPa * s or less. Isocyanate group terminal obtained by reacting one or more polyoxyalkylene polyols (a) selected from polyoxyalkylene polyols having a number average molecular weight of 4000 to 12000 and an average hydroxyl number of 2 to 3 with tolylene diisocyanate. Number average molecular weight of 4000 to 12000 obtained by reacting a prepolymer and one or more alkylene oxides selected from propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide and ethylene oxide with an initiator , average Polyoxyalkylene polyol having 2 to 3 hydroxyl groups (b) [However, at least one of (a) and (b) has an average hydroxyl group number exceeding 2. Comprising a plasticizer-free two-component curable composition for various rolls, vibration isolator or shock absorber,
The polyoxyalkylene polyol (a) and polyoxyalkylene polyol (b) used in the production of the prepolymer are prepared using a zinc hexacyanocobaltate complex catalyst, and the total unsaturation is 0.03 meq / g or less. And
A two-component curable composition which provides the polyurethane elastomer molded article according to claim 1 .