JPH07173442A - Biodegradable pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To provide the title adhesive excellent in pressure-sensitive adhesiveness and in biodegradability by mixing a raw rosin with a natural rubber in a specified ratio. CONSTITUTION:This adhesive comprises 100 pts.wt. raw rosin and 40-240 pts.wt. natural rubber. This adhesive is is of a type of latex or hot melt adhesive. Examples of the raw rosins include gum rosin, wood rosin and tall oil rosin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a pressure-sensitive adhesive, which has a degradability by microorganisms.

[0002]

2. Description of the Related Art After the war, the development of adhesives was based on rubber-based adhesives as a main pillar, and the polymers developed one after another were thoroughly tested and applied to products. Polyvinyl acetate adhesives have been evaluated comprehensively in terms of practicality and functionality, and these are found in Japanese Patent Publication Nos. 26-5640 and 27-530,531. . From the raw material situation of Japan at that time and the technical accumulation after the war,
Vinyl acetate was an affordable raw material. Then, the special public Sho 28
No. 6041 discloses an adhesive based on vinyl chloride / vinyl ether copolymer and vinyl acetate.
In JP 47, a polyvinyl butyral adhesive is found. After that, from 1955 onward, raw materials were imported and domestically produced, and various polymers found in European and American patents (eg polyvinyl ether, polyisobutyl, SB
Adhesives based on R, various synthetic rubbers, etc.) have been applied to products one after another. Particularly notable patents are Japanese Patent Publication No. 34-9270 and Japanese Patent Publication No. 35-35.
It is the advent of acrylic pressure-sensitive adhesives starting from Japanese Patent No. 4876 and Japanese Patent Publication No. 37-1471.

This acrylic adhesive has 2 to 2 carbon atoms.
12. A pressure-sensitive adhesive mainly composed of a (meth) acrylic acid ester of an aliphatic alcohol, and an acrylic resin as a main component obtained by copolymerizing a small amount of a monomer having a polar group including acrylic acid and acrylic amide. Is. Acrylic ester imparts tackiness, and other monomers are copolymerized to impart cohesiveness, adhesiveness, and further crosslinking reactivity. Almost no additional components such as tackifier resin and plasticizer are required.
Alternatively, a system obtained by reacting this with a cross-linking agent can serve as an adhesive. In other words, one component has viscoelasticity suitable for an adhesive. When such a pressure-sensitive adhesive is used for a biodegradable plastic container, a paper label, or the like, it does not decompose and remains as a lump in a landfill or a river lake, causing a problem.

[0004]

The conventional containers such as shampoos have a problem in treating the used ones. That is, since the plastic container is chemically very stable, the only option was to burn it in a special incinerator or fill it up as it was. Landfilling is not preferable due to the problem of environmental pollution, etc., as the interest in landfilling has been increasing in recent years. Therefore, biodegradable plastics have recently received worldwide attention as one of the solutions to the global environmental problems by waste plastics. This biodegradable plastic has come to be used for plastic containers and the like. However, until now, the pressure-sensitive adhesive for adhering a label or the like to this biodegradable plastic container has not been biodegradable.

[0005]

The present invention was devised in order to solve such a problem.
The purpose is to provide an adhesive having degradability.

The present invention relates to a biodegradable adhesive comprising 100 parts by weight of raw rosin and 40 to 240 parts by weight of natural rubber. Furthermore, the present invention relates to a pressure-sensitive adhesive in which the pressure-sensitive adhesive is in a latex form. Furthermore, the present invention relates to a pressure-sensitive adhesive in which the pressure-sensitive adhesive is a hot melt type.

The natural rubber used in the present invention is produced by collecting an emulsion (latex) obtained by damaging the bark of Hevea brasiliensis, and filtering, coagulating, rolling, smoking, draining, and drying with hot air. The main component is cis-1,4-polyisoprene. Depending on the manufacturing method, there are smoked sheet, pale crepe, and hevea crumb, all of which can be used as the biodegradable adhesive of the present invention. The natural rubber latex used in the present invention is obtained by collecting an emulsion (latex) obtained by damaging the bark of Hevea brasiliensis and stabilizing it with ammonia. When observing the fresh latex with a microscope, rubber particles of different sizes and different sizes are actively moving in brown. The rubber particles are surrounded by a protective film of protein, the surfaces of which are negatively charged and repel each other, which keeps the latex colloidal system stable. The size of the latex particles is 0.1 to 0.5 micron in diameter.

The surface of the rubber particles in the latex is protected by being covered with a layer of phospholipid and protein.
This protective layer plays an important role in determining the stability and colloidal behavior of the latex. The bond between rubber particles, phospholipids and proteins is fairly strong, but
It is a well-known fact that it is 1,4-polyisoprene, and the number average molecular weight is about 100,000 to 1,000,000. Latex collected from trees has a rubber content of 30 to 40% and is uneconomical because it is uneconomical to transport it to the place of consumption, so the rubber content is concentrated to 60 to 70%. The concentration method includes a centrifugation method, a creaming method, an evaporation method and an electric gradient method. Fresh latex is generally neutral and has a pH of 7, but if left unattended, it will become acidic due to the action of bacteria and enzymes, resulting in a pH of 5
It spontaneously solidifies in the vicinity. In order to prevent this, ordinary natural rubber latex is concentrated and then ammonia is added to maintain pH 9 to 10, that is, alkalinity. Even in a stable state where ammonia is added, phospholipids and proteins are gradually decomposed, but higher fatty acid soap is produced and protected in the rubber particle protective layer, so that stability is not changed. In addition, natural rubber that has been subjected to a crosslinking treatment such as vulcanization has low biodegradability.

The natural rubber-degrading bacterium is a bacterium that lives in general soil and is not a special bacterium. Decomposing bacteria of natural rubber are Doi et al. (Japanese Patent Publication No. 63-5426, Journal of the Japanese Society of Agriculture, 65, 9).
81 (1991), Appl. Environ. Mi
crobiol. 50,965 (1985)), it is known to belong to the genus Nocardia or the genus Rhodococcus.

Raw rosin used in the present invention is P
It is collected from various species of the genus inus, and can be classified into three types according to the method of collection. The first is gum rosin, which is obtained by steam distillation of pine resin obtained by cutting the bark into V-shapes and removing the light fraction. The second is wood rosin, which is obtained by solvent extraction of pine stumps. The third is tall oil rosin, which is obtained by collecting and fractionating sludge from a paper mill. Raw rosin contains 90% or more of resin acid and 10
% Of neutral substances, and the main component of resin acid is abietic acid, levopimaric acid, neoabietic acid, parastophosphoric acid, etc. Gum rosin, wood rosin, tall oil rosin and the like can be used as the raw rosin of the present invention.

The composition of raw rosin and natural rubber is raw rosin 1
The natural rubber is used in an amount of 40 to 240 parts by weight, preferably 50 to 150 parts by weight, based on 00 parts by weight. If the natural rubber content is 50 parts by weight, especially 40 parts by weight or less, with respect to 100 parts by weight of raw rosin, tack and holding power decrease,
If the amount is 150 parts by weight, especially 240 parts by weight or more, the peel adhesive strength is reduced. In the present invention, as a filler, a softening agent, an antiaging agent, calcium carbonate, clay, zinc oxide, titanium dioxide, process oil, extender oil,
Polyisobutylene, polybutene, liquid polyisoprene,
It is safe to add 2,6-di-butyl-4-methylphenol, styrenated phenol, 2,5-di-t-butylhydroquinone and the like. The present invention is applied to an adhesive which needs biodegradability.

[0012]

EXAMPLES The pressure-sensitive adhesive of the present invention will be described below with reference to examples. In the examples, “part” means “part by weight” and “%” means “% by weight”. Example 1 Biodegradable sample of rosin Raw rosin (Chinese rosin) Rosin ester Hydrogenated rosin ester Dibasic acid modified rosin ester Polymerized rosin ester A microbial suspension from soil was prepared from Hokkaido, Akita prefecture, Miyagi prefecture,
Bacteria contained in the soil were extracted from Ibaraki, Chiba, Tokyo, Gunma, Shizuoka, Ehime and Okayama prefectures and used. As the growth medium, a synthetic medium composed of inorganic salts shown in Table 1 was used. To 40 ml of this medium, 30 mg of raw rosin powder and 0.06 of microbial suspension
Add milliliter and incubate. Culture at 30 ℃ 14
After that, the shaking was carried out while aeration was repeated 250 times / minute.

[0013]

[Table 1]

Comparative Examples 1 to 6 As comparative examples, only raw rosin without a bacterium (Comparative Example 1), only bacterium without a rosin (Comparative Example 2), rosin derivative (rosin ester, hydrogenated rosin ester, Dibasic acid-modified rosin ester, polymerized rosin ester) + bacteria (Comparative Examples 3 to 6) were used in the same manner. Measurement items 1) Measurement of organic carbon (TOC) in the culture broth The culture broth which had been cultured for about 80 days was subjected to 0.45 μm filtration to remove suspended solids, and then appropriately diluted to measure TOC. 2) Measurement of the number of bacteria About a culture solution that was cultured for about 80 days and diluted 1 to 100,000 times, it was cultured in a medium (hereinafter referred to as NB agar plate medium) in which agar was mixed with (Nutrient Broth manufactured by DIFCO). Then, the viable cell count per milliliter was measured.

Results 1) The TOC value shows the carbon content of the rosin component dissolved in the aqueous solution. The TOC value of Example 1 containing the bacteria was smaller than that of Comparative Example 1 because the dissolved rosin was decomposed. 2) It can be seen that in Example 1 containing the bacteria, the number of bacteria increased about 100 times as compared with Comparative Example 2 because the bacteria were grown with rosin as a nutrient source. 3) Since the rosin derivative is not biodegradable, the rosin derivative + bacteria system is the same as that of Comparative Example 2 from the measurement of TOC concentration and the number of bacteria. That is, it can be seen that there is no growth of microorganisms. From the above, it can be seen that there is no rosin derivative that biorosin has biodegradability.

[0016]

[Table 2]

Examples 2 to 6 Biodegradable Samples of Natural Rubber Natural Rubber Pale Crepe (Mixing 10 Times, 0 Times) Smoked Sheet Hevea Clam Natural Rubber Latex (A dry mass of natural rubber dispersed in water was used.) The culture solution was prepared in the same manner as in Comparative Example 1, and the natural rubber (7
This was done by adding 0.5 g of lumps (sterilized with 0% ethanol). Measurement items 1) Weight measurement Relative humidity 5 for initial and post-treatment weight measurement.
The humidity was adjusted to 0 ± 5% at a temperature of 23 ± 2 ° C. for 48 hours or more, and then the measurement was performed. The above-mentioned natural rubber sample which had been cultured for 40 days was washed with water so as not to damage it, dried and then weighed. The measured value was measured up to mg, and the weight retention rate was calculated for each sample by the following formula. Weight retention rate = 100 × (W2 / W1) (%) ... Equation (1) where: W1: weight before culturing W2: weight after culturing 2) change in molecular weight Analytical method: GPC (Gel Permeation C)
chromatography) Sample preparation method: Dried natural rubber was dissolved in THF, and only the soluble portion was measured. result

[0018]

[Table 3]

1) It was found that the weight of the natural rubber in the culture solution containing the microorganism was reduced by about 10% as compared with the natural rubber alone. This decrease is considered to be due to microbial decomposition. 2) It was found that the molecular weight of natural rubber was clearly reduced.

Examples 7 to 9 Natural rubber (pale crepe, masticated 10 times) and green rosin were sufficiently mixed in a ratio of Table 4 using toluene as a solvent, and then dried on a PET film to give a thickness after drying. A polyethylene coated high-quality paper (hereinafter referred to as a release liner), which was coated so as to have a thickness of 30 μm and dried at 90 ° C. for 2 minutes, was laminated to obtain an adhesive sheet. The pressure-sensitive adhesive sheet thus obtained was evaluated for pressure-sensitive adhesive properties (peel adhesion, tack, holding power) and biodegradability (proliferation of microorganisms, soil burial) as follows, and the results in Table 4 were obtained.

Peeling Adhesive Strength The obtained pressure-sensitive adhesive sheet was cut into a size of 25 mm width and 100 mm length, the release liner was then peeled off, and the resulting pressure-sensitive adhesive surface was polished with # 280 sandpaper. SUS304) and then bonded back and forth once with a 2 kg roll and left for 20 minutes, then at 25 ° C. relative humidity 65
% Peeling speed was measured at a peeling speed of 300 mm / min. Tack: The largest ball that stops the release liner of the obtained adhesive sheet on the slope of 30 degrees, sets the release surface, and stops within the running distance of 10 cm under the condition of 25 ° C and relative speed of 65%. The number was measured. The ball number is 5
It is displayed with a numerical value that is 32 times as large as the 20 types of "ball designation" from / 32 to 24/32. Holding power The obtained pressure-sensitive adhesive sheet was cut into a size of 25 mm in width and 50 mm in length, the release liner was peeled off, and the 25 mm wide and 25 mm wide portion of the resulting adhesive surface was sandpaper # 2.
Stainless steel plate polished by 80 (SUS304)
Then, the distance (mm) at which the pressure-sensitive adhesive sheet fell off the stainless steel plate with a load of 1 kg was measured.

Proliferation of Microorganism The method for preparing the microbial suspension was carried out in the same manner as in Example 1. The culture was carried out by cutting out an adhesive sheet into a size of 5 mm × 30 mm and adding 0.06 ml of the microbial suspension to 40 ml of this inorganic salt medium. Culturing was carried out at 30 ° C. for 14 days, and shaking was carried out 250 times reciprocating / min while aeration. The growth of the degrading bacteria of the adhesive was confirmed by the presence or absence of cloudiness due to the growth of microorganisms in the culture solution.

Soil burial The burial site was set on a horizontal land that was manageable and as close to the natural environment as possible. Weeding and pebbles were removed from the burial site before burial. About 10 cm of the soil before burying was taken out from the surface, and it was hung on a sieve to make it as homogeneous as possible. Half of the homogenized soil was regenerated and the surface was lightened. 30m
A sample of m × 100 mm was placed on the ground surface without bending or wrinkling. The soil was homogenized with the remaining amount of soil, and the surface of the soil was lightened so that the sample was located about 5 cm below the surface of the soil. The buried place was left untouched in the natural state without weeding during the test period. After 46 days, the sample was dug up, and the weight retention rate of the sample was investigated by the formula (1). result

[0024]

[Table 4]

According to Examples 7 to 9, the adhesive property was good and the result was biodegradable. Comparative Examples 7 to 9 As a comparative example, an adhesive made of a synthetic material and raw rosin 100
Comparative Example 7 shows the adhesive property and biodegradability of an adhesive comprising 300 parts by weight of natural rubber and 30 parts by weight of natural rubber with respect to parts by weight.
~ 9.

Examples 10 to 12 The ratio of raw rosin dissolved in an organic solvent (cyclohexane) in natural rubber latex (35 wt% water dispersion system) is shown in Table 4 (the ratio of latex shown in the table is a substantial natural rubber component). ) Is thoroughly mixed and then coated on a PET film so that the thickness after drying becomes 30 μm, dried at 90 ° C. for 2 minutes and treated with silicone to give a polyethylene-coated high-quality paper (hereinafter referred to as a release liner). Were piled up to obtain an adhesive sheet. About the obtained pressure-sensitive adhesive sheet, pressure-sensitive adhesive properties (peel adhesion, tack, holding power), biodegradability (growth of microorganisms,
(Soil burial) was evaluated as follows, and the results in Table 5 were obtained. The adhesive property and biodegradability tests were carried out in the same manner as in Examples 7-9. According to Examples 10 to 12, the adhesive property was good and the result was biodegradable.

[0027]

[Table 5]

Comparative Examples 10 to 11 Comparative examples were carried out in the same manner as in the examples.

Examples 13 to 15 Natural rubber and raw rosin were used at a ratio shown in Table 6 to sufficiently heat mix them, and then hot-melt pressure-sensitive adhesives were prepared. This is P
Adhesive properties of adhesive tape applied to ET film (peeling adhesion, holding power), biodegradability (proliferation of microorganisms, embedding in soil)
Was evaluated and the results shown in Table 6 were obtained. The adhesive property and biodegradability tests were carried out in the same manner as in Examples 7-9. As shown in Table 6, those of Examples 13 to 15 had good adhesive properties (peeling adhesive strength, holding power) and showed the result of having biodegradability.

[0030]

[Table 6]

As a comparative example, 100 parts by weight of SIS (polystyrene-polyisoprene block copolymer) was used as a tackifier, Alcon M 90 (hydrogenated product of aliphatic hydrocarbon polymer, softening point 90 ° C. Arakawa Chemical Co., Ltd.). Made) 120
The adhesive properties and biodegradability of the hot-melt pressure-sensitive adhesive consisting of parts by weight are shown in Comparative Examples 12 and 13.

[0032]

The adhesive of the present invention has biodegradability and excellent adhesive properties. Further, an adhesive whose treatment is regarded as a problem is decomposed by microorganisms and used as an adhesive effective for environmental problems.

Claims (3)

[Claims] 1. 100 parts by weight of raw rosin and 40 to 40 parts of natural rubber
A biodegradable adhesive consisting of 240 parts by weight. 2. The pressure-sensitive adhesive according to claim 1, which is in the form of a latex. 3. The pressure-sensitive adhesive according to claim 1, which is a hot-melt type.