JPH07324140A - Biodegradable sheet and its production - Google Patents

Abstract

PURPOSE:To provide a cheap biodegradable sheet having properties such as practical strengths, being excellent in shock absorbing properties, water absorption, water retentivity, etc., and suitable for use in the field of life-related materials with soft touch particularly packaging materials and sanitary materials, by using a nonmeltable biodegradable fiber such as pulp and a water- insoluble thermoplastic biodegradable polymer as the base materials. CONSTITUTION:This sheet is one comprising nonmeltable biodegradable fiber A uniformly dispersed in a matrix of a water-insoluble biodegradable thermoplastic polymer B and water-soluble biodegradable polymer C, wherein the volume ratio of component A to component B is (10-80):(90-20), and the content of component C is 0.01-10wt.% based on the total of components A and B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable sheet suitable for use in the fields of daily life related materials, particularly packaging materials and sanitary materials, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, biodegradable polymers have attracted attention as "earth-friendly materials", and it has been proposed to use them as packaging materials. However, such a biodegradable polymer has a problem that it is generally expensive. Japanese Unexamined Patent Publication (Kokai) No. 5-311600 proposes a biodegradable sheet in which polycaprolactone and cellulose fibers are combined. According to this, the problem that the biodegradable polymer is expensive can be alleviated by using an inexpensive cellulose fiber such as pulp together. However, this sheet is obtained by combining a cellulose fiber sheet (paper) with polycaprolactone by a coating method, a film laminating method, a melt pressure bonding method, or the like, and is not suitable for some applications.

[0003]

The present invention is mainly composed of non-melting biodegradable fibers such as pulp and water-insoluble thermoplastic biodegradable polymer, and has physical properties such as strength for practical use,
Provide a low cost biodegradable sheet suitable for use in the fields of life-related materials that are excellent in shock absorption, water absorption, water retention, etc. and have a soft touch, especially packaging materials and sanitary materials, and a manufacturing method thereof. Is what you are trying to do.

[0004]

The present invention solves the above-mentioned problems, and the gist thereof is as follows. 1. A sheet containing a water-soluble biodegradable polymer C in which a non-melting biodegradable fiber A is uniformly dispersed in a matrix of a water-insoluble biodegradable thermoplastic polymer B having a melting point of 200 ° C. or lower, A biodegradable sheet, wherein the volume ratio of A to B is 10 to 80:90 to 20 and the content of C is 0.01 to 10% by weight of the total of A and B. 2. Non-melting biodegradable fiber A, water-insoluble biodegradable thermoplastic fiber Bf having a melting point of 200 ° C. or less and water-soluble biodegradable polymer C are mixed to form an aqueous dispersion, which is paper-formed and dried to form a sheet. And a method for producing a biodegradable sheet, which comprises subjecting the obtained sheet to heat compression molding at a melting point of Bf plus 30 ° C or higher and a temperature of 250 ° C or lower.

The present invention will be described in detail below. Examples of the non-melting biodegradable fiber A in the present invention include pulp, cotton, wool, regenerated cellulose fiber, solvent-spun cellulose fiber and the like, but pulp is preferably used because it is the cheapest. The pulp may be virgin pulp from wood or pulp recovered from waste paper.

Representative examples of the water-insoluble thermoplastic biodegradable polymer B in the present invention include aliphatic polyesters and aliphatic polyesteramides. Specific examples of the aliphatic polyester include poly (α-hydroxycarboxylic acid) such as polyglycolide and polylactide, poly-ε-caprolactone, poly-β-propiolactone, poly-3-hydroxypropionate, poly- 3-hydroxybutyrate, poly-3-hydroxycaprolate, poly-3-hydroxyheptanoate, poly-3-hydroxyoctanoate, and poly-hydroxyoctanoate
Polyhydroxyalkanoates such as copolymers with 3-hydroxyvalerate and poly-4-hydroxybutyrate, polyethylene oxalate, polyethylene succinate, polybutylene succinate, polybutylene adipate, polybutylene sebacate, polyhexa Examples thereof include condensation products of glycols and dicarboxylic acids such as methylene sebacate, polyneopentyl oxalate and copolymers thereof (including those having a chain-extended urethane bond with a diisocyanate compound). Further, specific examples of the aliphatic polyester amide include a co-condensation polymer of poly-ε-caprolactone and an aliphatic polyamide such as nylon 6.

Further, the water-soluble biodegradable polymer C in the present invention is preferably solid at room temperature, specifically, natural polymers such as fusuma, casein, and Trolo mallow.
Examples thereof include modified cellulose such as carboxymethyl cellulose and synthetic polymers such as polyethylene glycol and polyvinyl alcohol. Among them, polyethylene glycol is preferable, which is preferable because it exhibits water absorption without being affected by salt concentration when it is used as a sheet for sanitary materials.

The water-insoluble thermoplastic biodegradable polymer B needs to have a melting point of 200 ° C. or lower. If the melting point is too high, the temperature must be raised when the sheet is hot-compressed, and the non-melting biodegradable fiber A coexisting is discolored or deteriorated, which is not preferable.

The water-insoluble thermoplastic biodegradable polymer B as described above is generally hydrophobic and has little compatibility with the non-melting biodegradable fiber A such as pulp during molding. By adding water-soluble biodegradable polymer C, C
Acts not only as a binder component, but also as a modifier for the resin surface and fiber surface, making it possible to improve the low physical properties, which were the drawbacks of conventional biodegradable sheets, and improve tensile strength. Become.

In the sheet of the present invention, it is necessary that the volume ratio of the non-melting biodegradable fiber A and the water-insoluble thermoplastic biodegradable polymer B is 10-80: 90-20. is there. If the amount of A is too small, the cost will be high and the physical properties of the sheet will not be obtained. On the other hand, if the amount of A is too large, the amount of B which will be the matrix component will be too small and the matrix component of B will be too small. The effect as above is not sufficiently exhibited, the workability of the sheet becomes poor, and it becomes difficult to obtain a processed product having a strength that can be used. The volume ratio of A and B is calculated from the respective densities of A and B and the mixed weight ratio of both.

The amount of the water-soluble biodegradable polymer C is A
It is necessary to set it to 0.01 to 10% by weight of the total of B and B.
If this amount is too small, the effect of addition will be poor, and if it is too large, the water resistance will be poor and it will be difficult to use it in a system containing water.

Next, the method for producing the biodegradable sheet of the present invention will be described. First, the non-melting biodegradable fiber A, the water-insoluble biodegradable thermoplastic fiber Bf, and the water-soluble polymer C are mixed to prepare an aqueous dispersion, which is made into paper and dried to form a sheet. At this time, the water-soluble biodegradable polymer C is prepared in advance as an aqueous solution of the water-soluble polymer in consideration of work efficiency.
It is preferable to adopt a method of adding the aqueous solution so that the desired addition amount is obtained. Since the amount of the water-soluble polymer added to the aqueous dispersion actually taken into the sheet is different from the addition amount, it is preferable to prepare a calibration curve in advance and adjust the addition amount based on it. .

In the present invention, the fibers mean fibers having an aspect ratio of 5 to 3000. Pulp and cotton usually have an aspect ratio in this range as they are, but the aspect ratio can be adjusted by cutting as necessary. The artificial fiber may be cut so as to have a predetermined aspect ratio in the manufacturing process. Fiber length is 1
It is suitable to set it to about 30 mm.

Next, the obtained sheet is heated and compression-molded at a temperature not lower than the melting point of the water-insoluble biodegradable thermoplastic fiber Bf plus 30 ° C. and not higher than 250 ° C. In the heat compression molding, the water-insoluble biodegradable thermoplastic fiber Bf is melted, and the non-water-soluble biodegradable fiber A is uniformly dispersed in the matrix of the produced water-insoluble biodegradable thermoplastic polymer B. This is for making a strong binding sheet. The heating temperature in the heat compression molding is the melting point of the water-insoluble biodegradable thermoplastic fiber Bf plus 30
It is necessary to keep the temperature above ℃ and below 250 ℃.
If this temperature is too low, the water-insoluble thermoplastic biodegradable polymer B does not exhibit sufficient fluidity, and a high-strength sheet in which the non-melting biodegradable fiber A is uniformly dispersed in the matrix of B is obtained. I won't. On the other hand, if the temperature is too high, the non-melting biodegradable fiber A coexisting with it is discolored or deteriorated. The pressure during heat compression molding is suitably 50 to 150 kgf / cm ² .

It is also preferable to provide a step of spraying an aqueous solution of the water-soluble biodegradable polymer C on the paper sheet. When an aqueous solution of the water-soluble biodegradable polymer C is sprayed, a sheet having C uniformly attached to the surface is obtained, and the effect of C is further improved. The concentration of the aqueous solution of the water-soluble biodegradable polymer C at the time of spraying may be within the range of an aqueous solution having a viscosity suitable for spraying, but it is usually suitable to be 5 to 50% by weight. . Although there are differences depending on the water-soluble biodegradable polymer C in water, an aqueous solution of less than 5% by weight has too low a viscosity that the aqueous solution diffuses by spraying so that C can be accurately attached to the sheet. On the other hand, when the aqueous solution exceeds 50% by weight, the viscosity becomes too high and gels or the aqueous solution cannot be sprayed.

[0016]

EXAMPLES Next, the present invention will be specifically described with reference to examples. The measurement and evaluation methods of characteristic values and the like are as follows. Tensile strength and tensile modulus were measured according to JIS K-7127. Flexural strength and flexural modulus were measured according to JIS K-7203. Biodegradability A sheet having a size of 1 cm × 6 cm was embedded in a soil having a depth of 10 cm, taken out after 3 months, weighed, and evaluated by the following three grades according to the weight reduction rate. ◎: Weight reduction rate of 80% or more ○: Weight reduction rate of 50% or more and less than 80% △: Weight reduction rate of 20% or more and less than 50%

Example 1 Beated pulp (LBKP manufactured by Hokuetsu Paper Mills, density 1.54 g /
cm ³ ), fineness 3 denier, length 5 mm (aspect ratio approx. 25
0) poly-ε-caprolactone (PCL) fiber (melting point 6
A pulp disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) at a rate of 0 ° C. and a density of 1.15 g / cm ³ ) was charged into the pulp disintegrator and stirred at a speed of 3000 rpm for 1 minute. Next, the obtained paper material is transferred to a paper machine (Kumagaya Riki Kogyo's rectangular sheet machine), and the surfactant is added.
After adding 0.1 g / l to form an aqueous dispersion containing pulp and PCL fibers, "Paogen" (polyethylene glycol-based water-soluble biodegradability manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added so as to have the content shown in Table 1. Polymer) aqueous solution, JIS-P-8209
Papermaking was performed according to the method. The wet web was passed through a press (made by Kumagai Riki Kogyo Co., Ltd.) for dehydration and then air-dried to produce a sheet having a size of 25 cm × 25 cm. Then, this sheet was cut into four sheets of equal size and overlapped, and a molding machine (Cold & Hot Press manufactured by Kitagawa Seiki Co., Ltd.) was used.
Heat compression molding at a temperature of 100 kgf / cm ² at the temperature shown in
A uniform sheet having a thickness of 0.4 mm was obtained. The characteristic values of the obtained sheet are shown in Table 1. (Nos. 6 to 7 are comparative examples.) The "paogen" content was determined by subtracting the weight of pulp and PCL fiber from the weight of the obtained sheet.

[0018]

[Table 1]

In Nos. 1 to 5 which are the examples of the present invention, sheets having good physical properties were obtained. On the other hand, N
In o.6, the amount of PCL is too small, so in No.7,
The tensile strength was low because it did not contain "paogen".

Example 2 A sheet was obtained in the same manner as in Example 1 except that 1 ml of an aqueous solution of "paogen" was sprayed on the sheet before heat compression molding. The results are shown in Table 2. (No.11
Is a comparative example. )

[0021]

[Table 2]

In Nos. 9 to 10 which are examples of the present invention, good sheets having improved physical properties as compared with Example 1 were obtained. On the other hand, No. 11 has excellent strength characteristics,
Since the content of "paogen" was too large, it was difficult to put it to practical use in a system containing a large amount of water.

[0023]

According to the present invention, non-melting biodegradable fibers such as pulp and water-insoluble thermoplastic biodegradable polymer are mainly used, and they have physical properties such as strength to withstand practical use and shock absorption. Provided is an inexpensive biodegradable sheet suitable for use in the fields of life-related materials having excellent properties, water absorbency, water retention, etc. and having a soft touch, particularly packaging materials and sanitary materials.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29K 105: 12 B29L 7:00

Claims (3)

[Claims] 1. A non-melting biodegradable fiber A is uniformly dispersed in a matrix of a water-insoluble biodegradable thermoplastic polymer B having a melting point of 200 ° C. or less and contains a water-soluble biodegradable polymer C. A biodegradable sheet, wherein the volume ratio of A to B is 10 to 80:90 to 20 and the content of C is 0.01 to 10% by weight of the total of A and B. 2. A non-melting biodegradable fiber A, a non-water-soluble biodegradable thermoplastic fiber Bf having a melting point of 200 ° C. or less, and a water-soluble biodegradable polymer C are mixed to prepare an aqueous dispersion, which is prepared by papermaking. Then, dry it into a sheet, and add the obtained sheet to the melting point of Bf
A method for producing a biodegradable sheet, which comprises heat compression molding at a temperature of 30 ° C or higher and 250 ° C or lower. 3. The method for producing a biodegradable sheet according to claim 2, wherein the aqueous sheet of the water-soluble biodegradable polymer C is sprayed on the sheet made into paper.