Method Of Preparing Yarn And The Like From Animal Hide

Abstract

Collagen fiber is obtained from limed animal hide by a process which involves reliming, treating with an enzyme, and finally, beating to loosen the fiber structure of the hide. The fiber structure is then opened mechanically to obtain collagen fiber. The collagen fiber obtained is readily spun into yarn or string. Either the collagen fiber or the spun collagen yarn or string is treated with modifying agents such as tanning agents to improve its characteristics. The collagen yarn and string may be used for a large variety of knitted and woven products.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a method of preparing collagen fiber useful for making yarn, string and the like, from animal hide, particularly from split hide pelt.

During the manufacture of leather goods such as bags, shoes, gloves and so forth, small cuttings are obtained which generally cannot be utilized for these products; these scraps represent a substantial waste to the manufacture.

The need for industrial fibers is steadily increasing with the expanding population and also with the increasing demand for manufactured goods. In order for a fiber to be useful industrially, i.e. be capable of being spun, it usually must be about 2 to 4 cm. long and be relatively uniform in length. In addition, industrial fibers, when woven or knit into material, should have desirable characteristics, for example, with respect to texture, durability, elasticity, moisture absorption and so forth.

SUMMARY OF THE INVENTION

The object of this invention is to provide a method for obtaining from animal hide, collagen fiber which may be manufactured readily into yarn, string and the like. Another object of this invention is to provide an economical method for converting scrap leather into useful collagen fiber.

It has been discovered that collagen fiber which may be spun into yarn and string and manufactured into woven and knit goods may be obtained from animal hide by means of the following process. According to the present invention, split pelt, obtained from the hide has been unhaired and limed is subjected to an after-liming treatment and then to treatment with an enzyme to loosen the fiber structure of the split pelt. The fiber structure of the pelt is further loosened by a mechanical treatment such as beating and is then opened into loose collagen fiber by means of a fiber opener. The collagen fiber may be processed with one or more protein modifying agents, which provide the peptide chain of the collagen fiber with cross linkages and change the physical properties, particularly the solubility of collagen, and then spun into yarn. Or, the collagen fiber may be spun into yarn first and then treated, as yarn, with a protein modifying agent.

DESCRIPTION OF PREFERRED EMBODIMENTS

The portions of material hide which are used preferably in this invention are the shoulder and belly sections rather than material from the butt, as the former portions can be more easily opened under the conditions of the present process and have longer collagen fiber. Ordinarily, split pelt obtained in separating limed hide into grain layer and split layer and scrap coming from the beamhouse process are used as material, in order that the cost of the finished products be as low as possible, because materials hitherto considered useless are employed.

The step of reliming or after-liming constitutes one of the important features of this invention. Preferably reliming is carried out using a solution of calcium hydroxide, commonly known as lime water, in turbid form, at a temperature of about 25.degree. to 30.degree. C.

It has been found that of the collagen fiber obtained according to this process, its distribution and the yield of the collagen fiber depend to a large extent upon the period of time of reliming or after-liming.

Shoulder portions of split steer hide which had been dehaired and limed as described in example 1 below were dipped for varying period of time in about 5 times their weight and of an after-liming solution, of 2 percent calcium hydroxide maintained at a temperature of about 25.degree. C. The effect of the time of reliming on the length of collagen fiber recovered is set forth in table 1 below.

TABLE 1

Relationship between the period of time after-liming and the length of collagen fiber and its distribution. ##SPC1##

It is apparent from table 1 that the most favorable after-liming period is 8 days. After-liming eliminates mucoides (glycoprotein) and soluble proteins other than collagen, and loosens the linkage between collagen fibers. It may also be observed under the microscope, that the orientation of the fiber is greatly changed by this treatment. The after-liming solution is removed from the pelt by agitating the pelt in a dilute solution of a weak acid, such as an ammonium salt of strong acid, for example, ammonium chloride or ammonium sulfate or an organic acid, for example lactic or acetic acid, and then the pelt is washed with water.

According to this invention, the pelt is then subjected to the action of an enzyme such as animal protease or bacillus protease. The treatment with a proteolytic enzyme is ordinarily carried out at a temperature of about 30.degree. to 35.degree. C. and requires about 20 to 60 minutes.

The influence of the enzyme-treating conditions, i.e., the amount enzyme "pu" (which stands for easier digested power) used, upon the length of collagen fiber and its distribution was also examined and the results are shown in table 2. Split pelts which had been dehaired and limed and then subjected to after-liming for a period of 8 days were used for these tests.

It will be understood from this table that the added protease of about 40-80 pu/g. (casein digestive power/hide substance) is suitable for the material after-limed for 8 days. The test was also carried out on the material after-limed for 2 days, but no appreciable difference in the effect of enzyme treatment was found.

TABLE 2

Relationship between the amount of protease added and the length of collagen fiber. ##SPC2##

The enzyme is removed from the pelt by washing with water. The excess water is then removed by wringing or squeezing and the pelt is dried. Usually drying is effected by soaking the pelt in an organic solvent having a high solubility for water, such as acetone, ethanol or methanol. The length of time for the drying operation varies considerably and may take from several hours to several days, or even a week or more.

It has also been found to be preferable, after drying the pelt, to age it in a zone of high relative humidity prior to the beating operation.

The influences of the length of the aging period, during which the enzyme-treated and dehydrated material is left as it is until the next beating operation to facilitate fiber opening, were examined and the results are shown in table 3. In carrying out these tests, and preferably, the pelt is permitted to age at a temperature of about 20.degree. - 25.degree. C. under a relative humidity of 85- 90 percent.

TABLE 3

Influence of the aging period before beating upon the opening time, short fiber or fragment content and recovery ratio. ##SPC3##

It is apparent from this table that a 2 week aging period is most favorable to the fiber-opening process.

Immediately after being dried, the split pelt has a moisture content of about 7 to 8 percent, but it absorbs humidity from the air as time passes and attains a moisture content of about 18 to 20 percent after 1 or 2 weeks. At the same time, contraction of the fiber structure, which was caused by dehydration with the organic solvent is relaxed. It is likely that these are the reasons that the time required for fiber opening becomes shorter, the recovery ratio of fiber becomes higher and that an excellent distribution of long fiber is attained after 2 weeks of aging.

On the other hand, when aged for a month or more, mucoides and soluble proteins remaining between collagen fibers solidify and the fiber-opening effect is reduced, due to the same reasons which cause a change of composition in the dried skin.

It has thus been found that according to this invention the best conditions for carrying out this process include the use of shoulder and belly portions of hide; reliming for 8 days; treating the split pelt with 40 pu/g. protease; carrying out the fiber opening about 1 to 2 weeks after dehydration.

The collagen fiber obtained by the process of this invention is flexible, yellow-white, above 2.5 cm. in length, about 0.05 mm. in thickness, and has a cottony or lintlike appearance and is easily spun. It can therefore be spun into yarn by means of conventional cup-throstle spinning machines.

In order to provide the collagen yarn with properties suitable for its applications, it must be processed by one or more improving or modifying agents. Such improving or modifying agents include: inorganic salts such as chrome complex salts and aluminum salts of high basicity, or vegetable and synthetic tannins or aldehydes such as formaldehyde and gluta aldehyde and in general, any conventional tanning agent may be used to improve the collagen fiber or yarn. For example, when the collagen is to be made white, the aldehydes or aluminum salts of high basicity may be used. To increase the thermal contraction temperature, the chrome complex salts may be used.

These improving or modifying treatments may also be applied to the loose cottony collagen fiber or webs before spinning, in which case the fiber-opening operation is again required.

The finished products are obtained after currying the yarn, or after the fiber has been improved as above. If the yarn or fiber is to be colored, this must be done prior to currying with the use of such dyestuff that adapts itself to the improver used on the yarn or fiber concerned.

When the chrome complex salts or aluminum salts of high basicity have been used as improver, acid dyestuffs may be used, while basic dyestuffs are desirable in the case of vegetable tannins.

The yarn produced by the present invention can be woven or knit easily, and the woven or knit goods so produced will suffer no change in properties after long use but will maintain the original desired properties, as the yarn itself includes those properties which are most favorable to the secondary products concerned. The products, as well as the yarn produced by this invention, absorb or discharge moisture very well and maintain a constant moisture content. Moreover, they have good elasticity, excellent texture and are strong and durable. It can therefore be said that they are suitable as materials for daily necessities, such as articles of clothing, acoustic instruments and buildings.

EXAMPLE 1

The shoulder portion of salted steer hide from North America was unhaired and limed under the following conditions:

Soaking: 30 minutes rinsing in water at 14.degree. - 16.degree. C., 16 hours slaking in water of about 5 times the quantity of the salted hide-- 20 minutes rinsing in water, brushing and 10 minutes rinsing.

Unhairing and liming: 24 hours dipping in lime-mixed solution comprising calcium hydroxide of 5.0 percent, sodium sulfide flakes of 2.5 percent and water of 450 percent at 22.degree. - 25.degree. C., and after unhairing 10 minutes rinsing in water, rebrushing and 24 hours dipping in 2 percent solution of calcium hydroxide, extraction of spread by splitting the limed pelt with a band knife machine. The above percentages were all calculated with reference to the weight of salted hide.

Reliming: The split pelt was dipped in 2 percent calcium hydroxide solution for 8 days at 25.degree. C. The amount of solution was about 5 times the pelt weight.

Deliming: The split pelt was then tumbled in a drum for 40 minutes together with ammonium chloride of 1 percent and water of 200 percent until the coloration due to phenolphthalein vanished completely, after which it was rinsed in water for 20 minutes.

Enzyme treatment: Bacillus subtilis protease of 40 pu/g. was added to the pelt in a drum and the drum was rotated for 20 minutes with a bath of 250 percent therein at 35.degree. C. Then the split pelt was washed in hot water for 10 minutes and subsequently in running water for 30 minutes.

Drying: After being dehydrated with a squeezer, the stock was dipped in refined acetone for a weak. The acetone was renewed once a day. After 3 days dipping, the elastic tissue on the inside was removed by shaving machine.

Aging: The dried split pelt was aged in a room having a relatively high humidity 85- 95 percent at a temperature of 20.degree. -25.degree. C. for 2 weeks.

Beating: The aged material was then beaten for 1 hour with the use of a stamp mill.

Opening: The material was opened by pressing it against needle cloth on which needles 5 mm. in length are set, the cloth being wound onto wooden rollers 3 inches in diameter and 5 inches in width, and rotating 1,300 r.p.m.

For the cottony collagen fiber opened by means of the above steps, the recovery ratio was 75 percent and the collagen purity was 95.97 percent. The fiber 2.8- 4.5 cm. in length comprised 75 percent of the recovered fiber and the mean length was 3.6 cm.

This collagen fiber was spun into yarn on a conventional cup-throstle spinning machine. Then the yarn was dipped in water for 6 hours so as to fully absorb water, and thereafter was dipped in three solutions of chromium sulfate having basicity of 33.3 percent, 42 percent and 52 percent one after another for 1 hour respectively.

The collagen yarn removed from the last bath was left untouched for 2 days. Then it was cleared of extra chromium sulfate by rinsing in water, adjusted to pH 4.2- 4.6 with sodium bicarbonate solution, dyed with acid dyestuffs at 60.degree. C. and curried by adding sulfate olive oil of about 3 percent.

The woven goods made of this yarn are soft and elastic, not easily affected by temperature fluctuations owing to their ability to absorb and discharge moisture and to absorb perspiration or the like quickly. Such woven goods are considered to be ideal for use as mats in automobiles.

EXAMPLE 2

The cotton-type collagen fiber obtained by the same procedure as in example 1 was dipped in water for 6 hours so as to fully absorb water. Then it was dipped in 3 percent solution of vegetable tannin, in acetone for 2 days and subsequently in 3 percent aqueous solution in vegetable tannin for 5 hours. Thereafter it was fully washed in water. The mass of fiber thus obtained was opened on a card machine and spun into yarn by the same method as in example 1.

The mat knitted from the strings comprising several strands of the said yarn was more comfortable than a conventional mat for a car seat.

While this invention has been illustrated by some specific examples, the invention is by no means limited thereto; many variations will occur to one skilled in the art, and such variations are within the scope of the present invention.

Claims

What I claim and desire to secure by letters patent is:

1. A method of preparing collagen fibers from limed animal pelts comprising providing a limed animal pelt containing collagen fibers, splitting said limed animal pelt into a split pelt, placing said split pelt in a calcium hydroxide solution maintained at a temperature between 25.degree. - 30.degree. C. to effectively loosen the fiber structure thereof and eliminate soluble proteins other than collagen contained therein, removing the calcium hydroxide solution from the split pelt, then treating the split pelt with an enzyme selected from the group consisting of animal protease and bacillus protease, beating the treated split pelt to further loosen the fiber structure thereof, opening the loosened fiber structure of the beat split pelt to obtain collagen fibers, and treating the collagen fibers with a tanning agent.

2. A method according to claim 1 wherein said split pelt is obtained from the shoulder and belly portions of limed hide.

3. A method according to claim 1 wherein said placing step is carried out for a duration of about 8 days.

4. A method according to claim 1 wherein said treating step is carried out from 20 to 60 minutes at a temperature within a range of from 30.degree. to 35.degree. C.

5. A method according to claim 1 wherein said enzyme is used in an amount of 40 to 80 pu per g. of said pelt.

6. A method according to claim 1 wherein said pelt is dried and then aged for a period of up to 2 weeks in a zone having a relative humidity, between 85- 95 percent prior to beating said pelt.

7. A method according to claim 1 in which said collagen fiber is spun into yarn prior to being treated with said tanning agent.

8. A method according to claim 1 in which said collagen fiber is spun into yarn after being treated with said tanning agent.

9. A method as according to claim 1 wherein said tanning agent is selected from the group consisting of chrome complex salt, aluminum salt of high basicity, vegetable tannin, synthetic tannin and aldehyde.