KR20020002362A - Softened comminution pulp - Google Patents

Abstract

The present invention provides a method for softening cellulose pulp without adversely affecting the absorbency of a cellulose fiber product by using a chemical softener or a debonding agent containing a composition of a lower alkyl acid ester or a cyclic ester of a polyhydroxy compound and a product thereof. Related to. The process of the invention can also be used in combination with plasticizers for cellulose such as glycerol, mono- and di-saccharides, glycols and oligomers thereof. The method of the present invention is to provide a cellulosic fiber that is easier to densify aerosol pads formed of fluff formation (fibrosis) and the resulting individual fibers.

Description

Softened crushed pulp {SOFTENED COMMINUTION PULP}

Highly functional absorbent products, such as premium baby diapers, adult incontinence treatment products and sanitary napkins, are typically formed from a liquid permeable top sheet and a cellulose fiber fluff absorbent nucleus located under a low density absorbent or surge layer. The absorbent layer acts as a barrier to prevent the liquid from passing back to the user's skin while allowing the liquid to pass through the reservoir and absorbent nuclei without difficulty. A liquid impermeable backing sheet, usually made of a plastic material, contains an absorbent liquid and is provided to prevent the liquid from passing through the absorbent nucleus and getting buried under the product wearer. The absorbent layer contains chemically curable cellulose fluff or bonded synthetic fibers and the fibers are joined by thermoplastic binder fibers or powder or by adding latex binder.

The absorbent nucleus of the absorbent article usually consists of de-fiber pulp with or without superabsorbent polymer particles. The absorbent nuclei are formed in the pad forming unit of the transducer on the transfer structure to facilitate processing. The absorbent nucleus forming unit has a lamination function in which a second separated fluff layer is also laminated on the first fluff-type absorbent layer to form a multi-layer absorbent structure. In this absorbent structure, the first layer contains superabsorbent polymer particles. As an example of a known absorbent structure, U. S. Patent No. 5,009, 650; 5,378,528; 5,378,528; 5,128,082; 5,128,082; No. 5,607,414; No. 5,147,343; 5,149,335; 5,222,810; 5,222,810; 5,041,104; 5,041,104; 5,176,668; And 5,389,181 and 4,596,567.

The manufacture of disposable absorbent hygiene products, in particular diapers and incontinence treated products, is generally carried out in a continuous production line in which cellulose fluff absorbent material is fed to a pulverized pulp roll. Pulp is produced by conventional wet lamination or similar machinery in which the pulp sheets are unwound in rolls and fed into a hammer mill to separate the cellulose fibers in the sheets into cellulose fluff. The skilled person using the process of the invention may or may not require a drying step before the hammer mill. The fluff is then conveyed to the formation to be air-laid in the amount and shape required for the final product.

For the softening of sheet products for efficient crushing treatment, the use of cationic surfactants as debonders to break the interfiber bonds has been the traditional method, thus making sheet products more soft and softer. . US Patent No. 4,432,833; No. 4,425,186; And 5,577,308 disclose examples of such debonders. A common drawback of conventional cationic binders is the loss of hygroscopicity or absorbency of the pulverized pulp due to the relatively cationic surfactant of the alkyl chain. Blocked hydrogen bonding sites soften the pulp sheet and thus more easily break up into fiber strands. Debonders also encourage the formation of towering, low-density structures that rise above the interfiber hydrogen bonds that inhibit permanent densification. Thus, it is advantageous to produce crushed products that are easily compacted for use in the final pneumatic or woven product.

Plasticizers for cellulose that can be added to the pulp slurry prior to forming the wet island sheet can also be used for softening pulp, but act by debonder and other mechanisms. Plasticizers act on the cellulose molecules in the fibers to soften or soften the amorphous regions. The resulting fiber is muggy. Because plasticized fibers lack strength, pulverized pulp is more easily densified compared to unplasticized fibers.

Plasticizers include polyhydric alcohols such as glycerol, polyglycols such as polyethylene glycol and polypropylene glycol, and other polyhydroxy compounds. This and other plasticizers are described in US Pat. No. 4,098,996; 5,547,541; And those described in US Pat. No. 4,731,269. Ammonia, urea and alkylamines are also known to plasticize wood products containing mainly cellulose. (A.J. Stamm, Forest Products Journal 5 (6): 413, 1955).

Plasticizing is intended to more easily densify the air-island nonwovens made from pulverized and treated pulp. The cellulose composition softening method of debonding the fibers in order to effectively pulverize the pulp fibers makes refibrillation and subsequent densification easier without reducing wettability and is a very advantageous but presently lacking technique.

The present invention claims the priority of US Provisional Application No. 60 / 112,887, filed December 18, 1998.

The present invention includes a debonding agent such as a lower alkyl acid ester or a composition containing a polyhydroxy compound and a cyclic ester of a polyhydroxy compound and a polyhydroxy-functional plasticizer, to soften cellulose pulp using a chemical softener. Method, products thereof and the like.

FIG. 1 shows a graph showing the change in tensile strength of pulp sheets treated with debonder propylene carbonate and 5, 10 and 15 wt% triacetin solution.

Figure 2 shows a graph showing the change in tensile strength of the pulp sheet treated with a debonding agent or a plasticizer alone or a mixture thereof, using propylene carbonate and dextrose as the debonding agent and plasticizer, respectively.

Figure 3 shows a graph showing the change in tensile strength of the fiber treated with a debonding agent or a plasticizer alone or a mixture thereof and propylene carbonate and glycerin are used as the debonding agent and plasticizer, respectively.

The present invention provides new methods and products for softening cellulose pulp using new chemical softener combinations that include both debonders and plasticizers. This softening converts the normal fluff pulp sheet into a sheet of soft fibers that are less compatible with each other. Thus, the resulting pulp is more likely to be fluffed (refiberized) and subsequently densified with aerospace pads of individual fibers after crushing. In addition, the absorbency and wettability of cellulose fibers are impaired by the softening treatment of the present invention.

Particles of the present invention using debonders and plasticizers can significantly reduce the energy equipment for converting pulp fiber sheets into absorbent products. However, the process of the present invention can reduce the production cost of products made from refibrillated pulverized pulp and result in low energy requirements, high efficiency and reduced wear of equipment. This is an unexpected surprising advantage of the present invention that has not been achieved until now by using only a general debonder or plasticizer to soften the pulp.

In one embodiment, the present invention provides a method for softening cellulose pulp comprising contacting the pulp with an aqueous solution containing a combination of a debonder and a plasticizer together.

In another embodiment, the present invention provides propylene carbonate, a new debonder for use only with debonders or in combination with plasticizers, in accordance with the method of the present invention for cellulose pulp softening.

The present invention is also directed to providing softened pulp prepared according to the method of the present invention for use in absorbent articles.

All references mentioned in the present invention are presented for reference. In the case of differences between the present application and the known art including terms, the contents of the application shall take precedence.

The softener, compound or composition herein includes any compound selected from debonders and plasticizers that can soften cellulose pulp. "Modified" pulp refers to treatment with or in contact with a softener.

The debonding agent for softening cellulose fibers of the present invention includes cyclic esters, alkylethers and arylethers of lower alkyl acid esters and polyhydroxy compounds, together with typical known cationic debonding agents.

Preferred debonders of the present invention include propylene carbonate, triacetin, propylene glycol diacetate, 2-phenoxyethanol and mixtures thereof.

Propylene carbonate, a cyclic ester of propylene glycol and carboxylic acid, is a high boiling point polar aprotic solvent and is widely used as a solvent for various polymers. (Eg, US Pat. Nos. 5,580,922; 5,554,657 and 5,629,227). The present invention has unexpectedly found that propylene is an effective cellulose fiber debonder without the side effects associated with the wettability or absorption of sheet-like pneumatic island products made from processed pulp. The debonding action of propylene carbonate is similar to that shown by acyclic esters of polyhydroxy compounds such as triacetin.

In one embodiment, the debonder of the present invention is used in combination with known plasticizers for softening cellulose. Plasticizers used in the present invention include urea substitutes such as polyhydroxy compounds, lower alkyl amines and diamines, urea, tetramethylolurea, mono- and di-saccharides, glycols and oligomers thereof. Preferred plasticizers include dextrose, glycerol and poly (ethyleneoxide).

Preferred debonder / plasticizer combinations are propylene carbonate and glycerol or other polyhydroxy compounds, triacetin and glycerol, as well as propylene carbonate and dextrose and the like.

Debinding agents and plasticizers of the present invention are those used commercially. Propylene carbonate from Huntsman, Houston; Triacetin and ethylene glycol diacetate are available from Eastman Chemical (Kingsport, TN); Glycerol is from Ashland Chem (Columbus, OH); Dextrose may be produced by each of Spectrum Bulk Chemicals (Gardena, CA).

In use, the softening composition may include both debonders and plasticizers, effectively debonding the fibers in the pulpsheet to reduce interfiber bonding and not affect subsequent densification processes. As a result, lowering of the tensile strength (indicative of the bond removal state) of the treated pulp sheet and the ease of crushing into individual fibers are achieved. The plasticizer of the softening composition penetrates into the fiber and softens or plasticizes it internally. As a result, it is possible to obtain dry absorbent articles which are easily-densified.

In the laboratory, it is most convenient to simply saturate the pulverized pulp sheet by dipping and light blotting with a softened aqueous solution. In the actual manufacturing process, there is a method of spraying a softening additive or feeding the pulp sheet directly before or after the sheet enters the drying step. Softening liquid may also be added to the pulp slurry prior to forming the sheet. The soft liquor can be sprayed on a pneumatic island production line or it can be added when the pulp sheet is released from the rolls and fed to a hammer mill or other crushing unit.

The amount of softening liquid to be added to the pulp sheet varies depending on the concentration of the additive in the treatment liquid and the target concentration required for the product. Treatment time is not critical (ie does not affect the softening properties of the treatment pulp) and can vary from seconds to days.

The treatment liquid may also contain 2-99% by weight debonder and plasticizer. Preferably the concentration in solution is in the range of 3-7% by weight.

Tensile Test Procedure of Sheet Material

The breaking strength of the anhydrous sheet-type cellulose strip was measured using a Twig Albert Intellect II tensile tester model 1450-24-A. Tensile strength is reported in pounds per inch of sample butterfly. The samples were cut in the sheet processing direction into strips of 4.5 × 1 inch size. If the fracture strength exceeds 100 lb / inch, the specimens of 1.5 cm butterfly are tested. Tensile testing is carried out in the laboratory under conditions of temperature and humidity of 23 6 1 ° C (73.4 6 2 ° F) and 50 6 5% (relative humidity), and the sample is allowed to equilibrate for at least 2 hours prior to testing. Make two or three duplicate measurements and average the results.

The properties of the softened cellulose pulp obtained can be tested according to the following procedure.

Decomposition Energy Measurement Procedure

At Buckeye Technologies, Inc., pulverized pulp sheets formed by conventional wet drawing methods are treated with a softening agent, re-dried if necessary, and sized 2 "x 30" in a 30 "machine direction. Cut into strips Crushed pulp is usually 700 g / m ² by weight, record each weight of each strip and feed each to a Kamas Industries AB Type KVARN H01 for disassembly. The screen is 16-17mm and rotates at about 3000rpm at 8ft / min speed Measures the power consumption required for decomposition and is usually expressed in KWH / tonne (kilowatt-hours / tonne of pulp) Residual water content and relative humidity in pulp The untreated control sheet strips also act as benchmarks for comparison each time a sample is measured. The rate of multiplication and decomposition energy can be applied to other standardized day.

Sample preparation method for absorption, strength and fluid transfer test of air felt

Cellulose fibers used in the test air felt pads are made of dry cellulose pulp purchased from Bouquete Technologies Inc. and treated with the softener of the present invention or processed into 700gsm sheets in an experimental paper machine (Dynamic Former, Inc.). Maintained without. The machine sprays the diluted pulp fiber slurry onto the high speed spinning drum to form a 8.5 "x 35" handsheet in the machine direction. The dry sheet pulp was converted to an airfelt containing no fiber mass by cutting the pulp into 2 " x30 " stripes. The strips were each fed to a Kamas Industries AB type KVARN H O1 experimental hand mill to form a uniform fluff.

Using a lab-sized padmaker mimicking a commercial pad molding method, a uniform dry fluff was airtapped in a controlled environment to form an air felt pad. The pads were placed in a padmaker for 4-5 minutes to overcome the effects of disintegrating the pulverized pulp in an uncontrolled atmosphere and the pads were exposed to a controlled environment and the controlled air was allowed to pass sufficiently through the pads. This method also overcomes the effects of compressed air at 50% relative humidity used in pad manufacture.

A 14-1 / 2 "x 14-1 / 2" tissue group was placed in a padmaker's molding screen. This tissue completely covered the forming screen and bent the slope. This tissue represents the bottom of the pneumatic island felt pad. Appropriate amounts of fluff samples were added to the padmaker in four equal increments using pads rotated 90 ° between each increment for uniform pad formation. After the fluff was added to the pneumatic island felt pad, the shaping screen was removed with the air felt pad and slowly converted to a smooth flat surface. The second cover tissue was marked and marked on the top surface of the pneumatic island air felt pad and mounted on top of the pad. A 14 "x 14" weight was placed in the pad in a manner that does not interfere with the formation of the air felt pad. The weight was placed in an air felt pad for at least 5 minutes and then carefully removed. The pads were cut into 12-3 / 4 "x 12-3 / 4" squares, with each corner equally removed from the standard papercut plate. Pneumatic island felt pads were stored at 23 ± 1 ° C (73.4 ± 2 ° F) and 50 ± 5% relative humidity until testing. The cover tissue of the 4-1 / 4 "x 4-1 / 4" size pad was removed well and the pad was placed in the lower half of the aluminum press plate. The press plates consist of two aluminum blocks of size 6 "x6" x1 ". One side of each block is 6" x6 "and is machined to form a perfect flat surface. Two corners on one press plate The assembly pin was fixed near the part, and a corresponding hole was formed in the other press plate to accommodate the assembly pin, and the upper half of the press plate was installed on the pad to be crimped, and the whole press plate was carver hydraulic press (model). No. 16600-224) Each pad is compressed to the required pressure to obtain the required density, since the pad size is obtained as a result of compression, the pads are chamfered to 4 "x 4" size and weighed respectively. Wait 120 seconds to delay rebounce and measure the thickness of each pad The density of the pad was calculated according to the following equation.

Density (grams / cc) for a 4 "x4" pad = 0.000379 x weight (gms) / thickness (inches)

Drip amount test method

In order to measure the absorbance of the absorbent structure made of the cellulose fiber treated with the softener of the present invention, an air felt pad was produced according to the above-described method. The fluid transfer force of each air felt pad was determined by measuring the amount of drips expressed in milliliters per gram of cellulose in the air felt pad without cover tissue. Instead of urine, a 0.9% NaCl solution was prepared by dissolving 9 grams of NaCl in 991 grams of distilled water. The burette was filled with saline solution and the flow rate of the pipette was adjusted to deliver 2 ml / sec of urine. The delivery tip attached to the burette's cock is located at a height of 1 "above the cube of 0.5" wire mesh. The cube is placed in a pan that will hold excess fluid. The top of the cube remains at a constant level position. did.

Immediately after compression to the appropriate density, pads were placed in the cube so that the fluid collision point was in the crosswire position. At the same time, the burette's cock was opened and the timer started. The test fluid was deposited at the center of the pad at a constant speed. The timer was stopped when the first drop on the pad was released and dropped on the pan. The time it took when the first drop passed the pad was recorded. The wet pad was removed from the cube and discarded. The cube was completely dry and returned to the pan. The method described above was repeated for two airfelt pads identical to the first in weight, density and composition. Weight, density and time were recorded for each of the three pads. The amount of drip on each pad was calculated according to the following formula and averaged with the others:

Drip amount (ml liquid / g sample) = time (seconds) x 2/4 "x4" pad weight (g)

How to measure total absorption

In order to measure the absorption of the absorbent structure made of the cellulose fiber treated with the softener according to the present invention, the air felt pad was prepared according to the above-described method. Absorption was measured on an air felt pad without covering tissue. 4 "x4" air felt pads of 300 gsm and 0.2 g / cc density were placed on a plastic sheet with weight and weighed. Pads and plates were placed on a 60 degree inclined platform. The pad was saturated with 0.9% NaCl. Excess liquid was drained and removed with blotter. Weigh the plate and saturated pad.

The total absorption is calculated as follows:

Absorption amount (g / g) = (Wet weight-Dry weight) / Dry weight

Collapse Strength Test Method

In order to indicate the collapse strength of the absorbent structure made of cellulose fibers treated with the binder removal agent according to the present invention, a pneumatic island air felt pad was prepared according to the present invention. An air felt pad containing debonded cellulose fibers or untreated cellulose fibers was prepared according to the method described above for use as a control pad. The collapse strength of each pad was determined by measuring the force required for the ball penetrometer of a typical tensile test apparatus to reach the tolerability point of the pad without tissue for covering.

The collapse strength of the air felt pads was measured using a Twin Albert Intellect II tensile tester. The tensile tester includes a clamp platform and a clamp plate, which is intended to hold the test pad in a horizontal position between the platform and the plate. The platform and the clamp plate are provided with corresponding holes to receive the ball permeables and the ball permeables are positioned directly above the hools. The tensile tester was set up in compression mode and attached to the gram cells to be monitored for resistance values to be counted by a 1.5 cm diameter ball permeator.

Immediately after compression to a density of 0.2 g / cc, the pad was placed in the hole of the clamp platform and the clamp plate was firmly clamped onto the pad to lock the pad in place. Start Intellect and adjust the crosshead to 0.5 in / min or 1.27 cm / min. When the ball penetrator moves downward to contact the pad, the always-increasing force reading continues to appear on the monitor. The permeator continues through the pad until it reaches the typical resistivity point that appears when the pad breaks. At the non-resistance point, the crosshead automatically rebounds to the initial position. The maximum value of the force displayed on the Intellect monitor was recorded. This method was repeated twice with a new air felt pad. These pad values were averaged and the maximum value of the force was recorded in grams.

How to measure vertical wicking rate

Air felt pads are densified to 0.1g / cc, cut into corners to 4 "x4" size, and are precisely installed between plastic plates with electronic moisture sensors. The storage timer automatically starts when the sample holder is lowered to 1/4 inch in the brine reservoir and the liquid level rises 1/4 inch above the reservoir level to contact the lower row of sensors. The timer also automatically stops when the front of the moving liquid reaches the top electrode (1.5 inches above the first row). Record the results in cm / sec.

Method for measuring inclined wicking rate of sheet cellulose pulp

In this test, an inch scaled plastic sheet is placed at an angle of 45 degrees to the vertical above the reservoir containing 0.9% NaCl liquid reddish with the usual food coloring. The pulp sheet (densified with an air island pad) is placed in a quarter-inch position in the reservoir and starts a stopwatch. Record the time that the advancing liquid tip reaches 3.5 inches. Create a table with the results in inches / second. In this experiment, the sheet-like pulp of Bouquets Technologies was put in distilled water, washed overnight and the pulp was hydrotreated again. The swollen sheet was passed through a nip roller to dewater on the felt of the paper machine and sprayed with a softener solution. The calculated amount of dry pulp and additional weight in the treated sheet, and additional amount calculated in terms of weight percentage ("addition%") were measured. In the following table, PC is propylene carbonate and G is glycerin. The warp wicking rate at any density is not affected by the softener treatment.

Decomposition Efficiency (DE) Measurement Method

This method is to determine the efficiency of decomposition or fluff formation of crushed pulp. This test measures the amount of degraded pulp that is sufficiently fibrous to pass through a 14-mesh screen (1.4 mm opening). For example, divide the fluff obtained from the Kamas laboratory hand mill exactly by 5.00 g. One 5.00g fluff group is transferred to a 14-mesh screen in a pressure-pneumatic separation chamber. The device includes a standard 8-inch diameter Tyler sieve, which has a transparent glass lid fixed on a clear plastic cylinder with an outlet mounted on the vacuum cleaner and one attached to a pressure gauge. The transparent plastic chamber also has a pneumatic inlet with a flexible coupling so that the compressed air flow can be oriented to thoroughly stir the fluff sample observed through the transparent plastic lid. Co-stirring with compressed air and decomposing pulp passing through the 14-mesh screen at a reduced pressure of 3 cm Hg removes the remaining portion of the screen after 2 minutes. Repeat this procedure for the second 5.00g fluff group. The weight is calculated by summing the second part retrieved from the screen. The weight of the decomposed lint is 10g minus the weight of the knit or fiber bundle recovered from the 14-mesh screen.

Degradation efficiency = 10g-weight of undecomposed lint / 10g x 100

The following examples are intended to illustrate the invention and the scope thereof is limited only by the claims.

Example

A control pulp strip was included in the experiment because the cellulose pulp had a natural residual moisture in proportion to the temperature and relative humidity in which it was stored and also in proportion to the strength of the fiber where it was most recently dried. This gained the initial weight and included a control pulp sample (without softening) allowing the calculation of the reaction amount or the addition of chemical softening to the pulp. The control was used to determine the moisture content of the starting material and thus can measure the actual weight gain of the treated sample.

In the following examples, the softener addition amount, ie the additive ratio to the treated sheet, was calculated by comparing the treated sample with a control strip in which the demineralized water was saturated and under the same dry conditions as the experimental treatment. The difference in weight between the first and dried controls is the difference between the final dry weight and the adjusted initial dry weight of the treated sheet divided by the final dry weight. In addition, the tensile strength in pounds per inch of pulp sheets treated according to the method of the present invention was measured in a conventional manner.

If the dissolved softener is rapidly absorbed by the pulp, the softener may separate from the blotted solution, resulting in a value greater than the expected load of the softener in the final pulp product. In other words, the excess solution is concentrated in the softener when water is inhaled more strongly into the pulp. If the softener is a humectant, the residual water content in the treated pulp may be larger than if the pulp was exposed to water only, thus resulting in a large weight gain of the pulp that is misunderstood as due to the treatment chemicals. Thus, in the following examples, the solution retained in the wet pulp contains the same softener as expected in the first solution.

Example 1

In this example, as shown in the table, a 1.5 x 6.0 inch (about 4.5 g) strip of Southern softwood kraft pulp sheet was saturated with a 5% aqueous solution containing softener and excess solution was removed by momentary blotting. . The strip was dried at 109 ° C. for 60 minutes.

The easy fibrosis treatment, which reliably indicates the debonding and softening treatment of pulp fibers, was evaluated using a laboratory blender operated at a constant rate and time for 0.7 g of modified pulp sheet samples. When the stirring blade of the blender is impacted and fully open, fluff gathers near the top of the blender, leaving the stirring blade. The sample turned completely fluff in the blender where possible, and then formed into a 2.25 inch diameter pad at a base weight of 390 gsm. The sheet density was measured after 10 seconds was pressed at 60 psi again at 30 psi.

Compared to the untreated sample, only the water treatment showed a slight weakening of the sheet, and the density of the air drop pad decreased as shown in Table 1.

Pulp treated with glycerol as a known plasticizer for cellulose showed a decrease in tensile strength, which indicates softening. However, this pulp is difficult to fiber in the blender because it takes more than 20 seconds to fiber. The sheet was pressed against a pad consisting of glycerol-treated fibers to obtain the dense sheet expected for the plasticized fibers.

Pulp sheets treated with triacetin or propylene carbonate (PC) have low tensile strength and easy fluffing, and extensive bond removal in the pulp sheets is supported by two test results.

Saturation of Pulp Sheet Pulp treatment Addition rate Tensile Strength (lb / in) Mixer, Fibrosis (sec) Air Island Density (g / cc) No treatment 0 107.1 20+ 0.24 water 0 94.9 20+ 0.21 glycerin 6.5 68.2 20+ 0.26 Propylene carbonate 5.0 52.8 10 0.23 Triacetin 5.4 45.0 10 0.21

In Example (2-5), the pulverized pulp sheet (Poly fluff; Bouquet Example Technologies) was cut in the machine direction to make 1.5 "x6.0" strips. The strip was about the closest number of milligrams (about 4.5 g) when weighed, and then saturated with the softening solution as described in each example. Excess treatment was discarded, the wet sheet was weighed and placed in a laboratory convection oven at varying temperatures to remove moisture.

Example 2 Plasticizers and Mixtures of Plasticizers and Debinding Agents

The pulpsheet strips were treated with a plasticizer and a mixture of plasticizer and aqueous propylene carbonate (debonder), as shown in Table 2. The pulp sheets were saturated with 5% solution of each softening component and one solution containing 5% of each component. 5% is the concentration of the solution. The sheet was placed in a convection oven at 109 ° C. and dried for 60 minutes.

The debonding effect was expressed as an additional percentage of the absorbed treatment liquid and was close to the additive containing a combination of propylene carbonate (PC) and dextrose. Combined all of these softeners were more effective as debonding agents of the pulp sheet than if they were used separately.

The sample treated with a mixture of glycerol and propylene carbonate had a slightly lower tensile strength than the average value of the sample treated with each component separately.

The treatment of the sample with urea, another known cellulose plasticizer, did not show significant debonding action. Samples treated with urea mixed with propylene carbonate showed tensile strengths comparable to the average of samples treated with each of these agents.

Plasticizers, Debinding Agents and Mixtures Pulp treatment % Addition Tensile Strength (lbs / in) Average Tensile Strength (lbs / in) Untreated Pulp Sheet 0 107.1 Dextrose 7.1 86.5 Propylene carbonate 5.0 52.8 Dextrose and Propylene Carbonate 11.5 43.4 65 Glycerol 6.2 69.2 Glycerol and Propylene Carbonate 8.1 57.7 61 Element 6.0 109.9 Urea and Propylene Carbonate 7.6 81.6 81.4

Example 3-Temperature Experiment

The drying temperature had no significant effect on the efficiency of propylene carbonate treatment or on the amount of fiber modification (softening). The pulp sheet was saturated with 5% aqueous propylene carbonate and dried at different temperatures as shown in Table 3. The efficiency of the softening treatment is expressed as the final dry weight gain value, which is a percentage of the amount of propylene carbonate added to the pulp in the wet stage.

Drying Temperature Test Temperature efficiency % Propylene Carbonate% 88 62.3 4.8 100 56.4 4.4 125 59.4 4.5 135 60.1 4.4 150 57.8 4.5

Example 4 Binder Retention Test

An experiment was conducted to determine the retention capacity of the organic ester debonder at the change temperature in the cellulose pulp. The pulp sheets were saturated with a 5% softener solution and dried in an 135 ° C. oven.

Experimental results show that cellulose pulp has a limit of absorbing and retaining organic ester debonding agent and its value varies according to softener and drying conditions. Weight gain of most samples occurred in the first treatment. Only a slight increase in debonder retention in the pulp was obtained during the second treatment. The pulp sample treated only with triacetin showed a greater total weight gain when the sample was first dried at 25 ° C. and again dried at 109 ° C. after each treatment. The total weight gain under these conditions was twice that of drying at 135 ° C. after triacetin treatment. The temperature had little effect on the weight gain of the sample treated with propylene carbonate (PC).

Debonder, Sequential Processing Primary treatment Weight gain% Secondary processing Gross weight gain Triacetin, 135 ° 4.2 Triacetin, 135 ° 4.3 Triacetin, 135 ° 4.24 Propylene carbonate, 135 ° 5.08 Propylene carbonate, 135 ° 4.4 Propylene carbonate, 135 ° 5.2 Propylene carbonate, 135 ° 4.5 Triacetin, 135 ° 5.03 Triacetin, 135 ° Not detected Triacetin, 109 ° 8.48 Propylene carbonate, 25 ° Not detected Propylene carbonate, 135 ° 4.75

Example 5-Debonder Loading

The pulp sheets were saturated with 5, 10 and 15% solutions containing triacetin or propylene carbonate, temporarily removed and dried in a convection oven at 135 ° C. for 60 minutes. Propylene carbonate is miscible with water and can vary the initial solution loading to pulp by varying the concentration of the treatment liquid. Triacetin had a limited solubility in water and was treated with 5% triacetin multiple times and replaced with 10 and 15% data values. See Table 5 and FIG. 1. The control treated with water is for rehydration. Final treatment levels were calculated as weight gain due to debinding agents which are a percentage of final weight.

As shown in FIG. 1, when the pulp was dried at 135 ° C., the pulp absorbed up to about 5% propylene carbonate or triacetin solution by weight of the treated pulp.

Binder Concentration at 135 ° C density Propylene Carbonate% Triacetin 0 0 0 One 0.8 One 2.5 2.6 2.2 5 4.7 3.4 10 4.7 4.3 15 4.9 4

Example 6-Tensile Strength / Additive Load

In this experiment, the pulp sheets were saturated with various dilutions of plasticizers, debonders, and 1: 1 mixtures thereof, and then the tensile strength of the pulp sheets as a function of the amount of denaturation was tested in lb / in. Additive loadings are expressed as weight percentages for the final pulp product. The results are shown in Table 6 and shown in the graphs shown in FIGS. 2 and 3. Table 6 is divided into three zones: plasticizers, debinding agents and mixtures thereof. The tensile strength of the pulp sheet indicates the bond removal effect. Plasticizers have been shown to significantly weaken the sheet on the glycerin side than dextrose. As the debonder, propylene carbonate and triacetin have a loading of up to 5.4% (upper limit of propylene carbonate addition). FIG. 2 shows the dextrose and propylene carbonate data in Table 6 and FIG. 3 graphically shows the glycerin and propylene carbonate.

Tensile Strength of Pulp Sheet as a Function of Additive Load Plasticizer Debonder Formulation Addition% glycerin Dextrose Triacetin Propylene Carbonate (PC) PC / dextrose PC / Glycerin 0 90.2 90.2 90.2 90.2 90.2 90.2 2.2 65.1 2.8 43.6 88 3.7 69.4 4.4 87 44.8 4.6 51.2 5 70.2 52.8 5.4 45 44.4 61.3 6.1 69.2 54.9 6.6 68.2 7.1 86.5 8.3 57.7 8.5 31.2 11.6 43.4 12.1 47.3 14.3 72.6 16.7 29.5

Note: As shown in the table intervals, not all formulations were tested at all treatment levels.

Example 7 Saturation of Pulp Sheets

Tensile force measurement is one method of measuring the binding effect of pulp additives. Internal strength tests on sheets of cellulosic fiber material are related to the carcass mill decomposition energy. In Table 7, the Kamas energy, tensile strength and decomposition efficiency of the treated pulp sheets were measured. Drying strips of crushed pulp (Bukeye Technologies) were treated by saturating the strips in each solution, removing the filtrate and drying in a 109 ° C. convection oven. In Table 7, propylene carbonate is abbreviated PC and triacetin is abbreviated TA and 200 molecular weight polyethylene glycol is E-200, respectively. Since the decomposition energy (KE) varies according to various variables, a control untreated pulp sheet was performed for each sample group. Samples are listed with reduced camas energy.

Decomposition Energy and Tensile Strength process Load rate% KE (KWH / ton) Tensile Strength (lbs / in) DE% none 0 30.2 101.3 89 water 0 27.3 93.4 94 1.25% PC / E-200 3.5 22.9 49.8 98 2.5% PC / E-200 6.5 21.0 45.4 96 1.25% TA / dextrose 3.9 20.5 47.8 97 1.25% TA / E-200 3.7 18.4 41.7 97 2.5% TA / E-200 6.4 16.8 35.2 97 2.5% TA / Dextrose 7.4 16.3 40.6 98

Treatment with water alone results in a pulp sheet that is significantly weakened in tension, decomposition energy and decomposition efficiency. The tensile strength of the sample shows a much more pronounced relative decrease than the decomposition energy upon treatment with the softener. Tensile strength is directly related to the decomposition energy. More concentrated treatment liquids provide lower energy and strength values.

Examples 8-10: Treatment of Rehydrated Pulp Sheets

Bouquet Example Technologies Co., Ltd. sheet-shaped cellulose pulverized pulp is soaked in distilled water overnight to rehydrate the pulp. The swollen sheet is passed through a nip roller to dewater on the paper machine felt and sprayed thereon with a softener solution. This procedure was used in two planned experiments (three levels and two variables) and also in two simple experiments (three levels of one variable) and mimics the process of processing dry pulp sheets without virtually making the sheets. It is. From the dry pulp calculated amount of the treated sheet and the weight of the wet additive, the weight percentage of the added amount calculated | required was calculated | required. In the following table, PC is propylene carbonate and G is glycerin. The dry sheet was cut into strips of 2 " x30 " size in the working direction supplied to the camas mill. The modified fluff samples prepared in the experiments listed in Table 8-10 were blown with 450gsm handsheets, densified into Carver presses and subjected to inclined wicking measurements (45 degree angle to vertical), as shown in Table 8. . Find the velocity from the time that elapses until the front of the advancing liquid reaches a 3.5-inch distance. In the planned experiment as shown in Table 9 and in the separate additive tests as in Table 10, the decomposition energy is recorded and the remaining end of the strip fed to the hand mill is subjected to the tensile test. Decomposition efficiency is measured and the densification ease is evaluated. After making 450gsm airfelt pads with fluff, the pads were pressurized at 5,000 lb pressure (312 psi) against a 4 "x4" pad in Carver Press. The thickness was measured and real density was calculated. The greater the resulting density, the more easily the fibers can be densified and maintained in that state. It is used to detect the presence of cellulose plasticizers.

Incline Wicking Study process Density (g / cc) Speed @ 3.5 "(inches / sec) No treatment 0.096 0.10 water 0.095 0.09 1.5PC-1.5G 0.110 0.10 1.5PC-1.5G 0.109 0.10 1.5PC-1.5G 0.104 0.10 1.5PC-1.5G 0.110 0.11 1.5PC-1.5G 0.118 0.11 1.5PC-1.5G 0.118 0.11 1.5PC-1.5G 0.108 0.11 1.5PC-1.5G 0.095 0.10 No treatment 0.200 0.11 1.5PC-1.5G 0.200 0.11 1.5PC-1.5G 0.220 0.11 1.5PC-1.5G 0.200 0.11

Dual Treatment of Rehydrated Pulp process Decomposition (KWH / ton) Tensile Strength (lbs / in) 5K density (g / cc) water 23.9 78.6 0.53 2.0 pcs-4.06G 19.9 51.4 0.60 2.02PC-2.02G 18.8 31.3 0.56 2.1 pcs-3.17g 18.8 51.5 0.58 3.06PC-2.04G 13.5 46.3 0.56 3.16PC-3.16G 17.4 33.3 0.60 3.28PC-4.37G 17.3 38.2 0.64 4.11PC-2.05G 16.2 37.0 0.57 4.2 pcs-3.16G 16.6 53.8 0.61 4.57PC-4.57G 15.1 32.6 0.62

Individual Additives for Rehydrated Pulp process Decomposition (KWH / ton) DE (%) Tensile Strength (lbs / in) Density (g / cc) water 18.8 85 74.7 0.48 2.0PC 12.5 91 48.6 0.52 3.0PC 10.8 89 52.7 0.50 4.0PC 16.4 92 48.4 0.55 5.0PC 11.5 89 47.6 0.51 2.0G 12.0 88 56.5 0.55 3.0G 23.1 91 50.5 0.59 4.0G 19.7 81 61.0 0.57 5.0G 19.0 85 59.8 0.61

Statistical analysis of the two-sided design experiments (Tables 8 and 9) shows the interaction between debinding agent and plasticizer. Treatment of the rehydrated cellulose pulp with propylene carbonate and glycerin did not affect the wicking rate of 0.9% saline in the densified puff pads. The kamas decomposition energy and tensile strength of the sheets are generally reduced using high level propylene carbonate and the density after 5,000 lb pressure is related to the amount of glycerin in the treatment solution. In Table 10, it can be seen that only the propylene carbonate treatment lowered the decomposition energy and tensile strength and the fluff formation efficiency was improved. Glycerin alone increased the decomposition energy in three of four samples and improved the fluff formation efficiency in only two.

Example 11 Treatment of Dry Cellulose Pulp

In the case where the softening treatment is carried out in the pulp mill in which the pulverized pulp sheet is to be produced, the treatment liquid may be added before sending the newly formed sheet to the drying step if necessary. This work is simulated by redispersing the dry pulp from the pulp mill into water and shaping the pulp sheet using a laboratory hand sheet forming machine. After the first dehydration step, the newly formed sheet is softened and then dried and cut into strips for normal use. As before, the composition of the softening agent is expressed as a weight percentage of the final product.

Treatment of Dry Pulp Treatment PC-Glyc. (wt%) Camas Energy (KWH / ton) Decomposition Efficiency (%) Density 5000 lbs (g / cc) Tensile strength (lbs / in) 2ml drop (ml / g) Absorption amount (g / g) Burst intensity (gram) Vertical Wicking (cm / sec) 0-0 16.8 87 0.50 58.1 2.7 18.3 134.3 0.53 3-4 12.0 95 0.62 28.1 2.3 16.6 120.5 0.57 3-0 10.0 94 0.53 44.8 2.6 16.8 122.5 0.52 0-4 9.0 87 0.59 45.5 2.0 16.5 129.2 0.47

* PC is propylene carbonate and Glyc. Is glycerin.

Dry pulp corresponds to the softening treatment of the present invention in the same manner as dry pulp. Propylene carbonate alone or in combination with glycerin removes sheet bonds, as demonstrated by low decomposition energy and high decomposition efficiency. Also, as can be seen from the tensile strength, the sheet to be degraded by glycerin alone can be effectively softened, but the decomposition efficiency has not been improved.

As expected in the above examples, the ease of decomposition (density of 450 gsm air felt after instantaneous compression under a pressure of 5,000 lbs) is a function of the presence of glycerin, a plasticizer for cellulose fibers. The vertical wicking test confirms that the organic binder decomposition agent of the present invention represented by propylene carbonate has no adverse effect on the fluid transfer capacity of the air-formed cellulose fiber structure. The water absorption during softening can be somewhat reduced, but some reduction is expected in that there are fewer treated fibers to take to reach the same weight as when not treated.

Example 12 Treatment of Dry Pulp Sheets

Other final absorbent articles have the advantage of varying the resolution. A flexible converter that produces a group of products that does not need to maintain a wide variety of pulp is to perform pulp modifications online. This is easily accomplished by spraying a small amount of softener concentrate onto the pulp just before feeding the pulp sheet to the hammer mill. The practical advantage of this approach is that the softening can be carried out in the converter plant, not just in the pulp maker. In the following examples, the amount of propylene carbonate and glycerin added per sheet is kept constant at 3 and 4%, respectively. The total amount of water in the sheet is adjusted from 12-20% in 2% increments.

Treatment of Dry Pulp Sheet process moisture% Decomposition Energy (KWH / ton) Decomposition Efficiency (%) Tensile strength (lbs / in) 5K density (g / cc) none 6.3 25.8 89 101.0 0.51 none 12 20.6 78 102.0 0.52 none 14 18.8 78 87.6 0.46 none 16 18.5 74 85.5 0.44 none 18 21 77 95.3 0.42 none 20 16.8 79 98.3 0.46 3PC-4G 12 19 90 65.9 0.57 3PC-4G 14 16.4 93 71.1 0.59 3PC-4G 16 15.5 91 51.1 0.56 3PC-4G 18 18.5 89 60.7 0.59 3PC-4G 20 18.1 87 55.5 0.59

Spraying on the pulp sheet just before hand milling results in a significant reduction in decomposition energy at the expense of decomposition efficiency. Mixtures of propylene carbonate and glycerin have the added advantage of not only reducing the decomposition energy but also reducing the decomposition efficiency (liquid formation). Tensile strength of sheets treated only with water is significantly greater than those treated with binders and plasticizers. 450 gsm air felt pads made of fluffed pulp treated with propylene carbonate and glycerin at the same amount of pressure can be made to greater density.

Claims (21)

A method for softening cellulose pulp in which the pulp is contacted with an aqueous solution containing a debonding agent and a plasticizer. The method of claim 1, The debonder is selected from lower alkyl acid esters of polyhydroxy compounds, cyclic esters of polyhydroxy compounds, alkylethers and arylethers, and the debonder is present in an amount of about 0.1 to 50% by weight relative to the cellulose fibers. Softening treatment method characterized in that. The method of claim 1, And the contacting step comprises spraying an aqueous solution containing 2 to 75 wt% debonding agent and 2 to 75 wt% plasticizer. The method of claim 1, Plasticizers are selected from lower alkyl amines, lower alkyls, lower alkyl diamines, urea, urea substituents, glycerin, mono- and di-saccharides, polyethylene glycols with molecular weights up to 1200, polypropylene glycols with molecular weights up to 1000, and And the plasticizer is present in an amount of 0.1 to 20% by weight relative to the cellulose. The method of claim 1, Debinding agent is a softening treatment, characterized in that selected from propylene carbonate, ethylene carbonate, triacetin, ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate and hydroxymethyl ethylene carbonate. The method of claim 1, The plasticizer is a softening treatment method, characterized in that selected from glycerol, dextrose and poly (ethylene oxide). The method of claim 1, The debonding agent is propylene carbonate and the plasticizer is glycerol. The method of claim 1, The debinding agent is triacetin and the plasticizer is glycerol. The method of claim 1, The debonding agent is propylene carbonate and the plasticizer is dextrose. Softened pulp prepared according to the method of claim 1. An absorbent article containing softened pulp prepared according to the method of claim 1. An absorbent product containing softened pulp prepared according to the method of claim 6. A method of softening cellulose pulp comprising contacting the pulp with propylene carbonate. Softened pulp prepared according to the method of claim 13. An absorbent article containing softened pulp prepared according to the method of claim 13. A cellulose pulp mixture comprising 3-7 wt% debinding agent and 3-7 wt% plasticizer. The method of claim 16, The cellulose pulp mixture is characterized in that the cellulose pulp has a decomposition efficiency of at least 96% and a carmasmill energy of about 22.9 KWH / ton or less. The method of claim 16, A cellulose pulp mixture, wherein the cellulose pulp, the debonding agent and the plasticizer are all contained in an aqueous solution. The method of claim 16, A cellulose pulp mixture, wherein the debonder is propylene carbonate and the plasticizer is dextrose. The method of claim 16, A cellulose pulp mixture, wherein the debonder is propylene carbonate and the plasticizer is glycerol. The method of claim 16, A cellulose pulp mixture, wherein the debonder is triacetin and the plasticizer is glycerol.