JPH07278510A - Biodegradable hot-melt type adhesive - Google Patents

Abstract

PURPOSE:To obtain an adhesive having the degradability with a microorganism without volatilizing a solvent in use by mixing a crude rosin with natural rubber and a wax at a specific ratio. CONSTITUTION:This adhesive is obtained by mixing (A) 100 pts.wt. crude rosin collected from various species of the genus Pinus of the family Pinaceae such as gum rosin, wood rosin and tall oil rosin with (B) 10-200 pts.wt. (preferably 20-150 pts.wt.) natural rubber and (C) 10-200 pts.wt. (preferably 20-100 pts.wt.) one or more vegetable or mineral waxes selected from castor wax, carnauba wax, candelilla wax, hardened soybean oil and paraffin, montan and rice waxes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot melt type adhesive characterized by having biodegradability.

[0002]

2. Description of the Related Art A hot-melt type adhesive is an adhesive which contains a thermoplastic resin as a main component and is solid at room temperature and has a solid content of 100%. It can be heated and melted in an applicator called an applicator, applied to the adherend in a molten state, and the bonding can be completed within a few seconds after pressure bonding. Sulfur, asphalt, wax, etc. have been used for a long time to obtain adhesive strength by heating, melting, and solidifying by cold heat.The hot-melt type adhesive here means workability at the time of bonding and adhesion. It is a multi-component adhesive containing a thermoplastic resin as a main component, the performance of which is sufficiently taken into consideration. Since the hot-melt adhesive does not contain water or a solvent, it does not require a drying time or a drying device, so that the bonding can be completed by pressure bonding in a short time after applying the adhesive. Due to these advantages, hot melt adhesives are widely used in all industrial fields today as being suitable for speeding up bonding work and eliminating pollution during bonding work.

The components constituting the hot melt adhesive include thermoplastic resins, tackifiers, waxes, etc.
Antioxidants and fillers are added as necessary. The ratio of each component is determined in consideration of workability (melt viscosity, open time, solidification rate, thermal stability, etc.) and performance (adhesiveness, heat resistance, cold resistance, etc.). The components and roles of the hot melt adhesive will be described below.

Thermoplastic Resin (Base Polymer) The base polymer conditions are that it has excellent cohesive strength, adhesive strength and flexibility, and that it has good compatibility with other resins. The most widely used ones at present are ethylene-vinyl acetate polymers (EVA), but include polyethylene, atactic polypropylene (APP), ethylene-ethyl acrylate copolymer (EEA), polyamide, polyester and the like.

Tackifier (Tackifier) The tackifier should have the conditions that it is compatible with the base polymer to impart hot tack property to the adhesive and at the same time lowers melt viscosity to improve workability during coating. It is a thing. As such a tackifier, a resin using a natural product such as a rosin derivative or a terpene has been mainly used, but a natural product is improved as the quality of a hydrocarbon resin such as a petroleum resin is improved. I became overwhelmed.

Waxes Waxes are used for lowering the melt viscosity of adhesives, and adjusting physical properties such as open time, softening point, hardness, hot tack property and blocking property. It is very convenient, but depending on the amount added, the adhesive strength is extremely lowered and the shrinkage rate of the adhesive is also increased.

The hot-melt type adhesive made of such a material does not decompose when used for a paper label, biodegradable plastic, etc., and thus remains as a lump in a landfill or a river lake, causing a problem. It was

[0008]

The conventional hot melt type adhesives are excellent in economical efficiency and safety and are used in mass consumption fields such as packaging, bookbinding, plywood and woodworking. . It is considered that adhesives suitable for environmental problems will be required in the future. For example, shampoo and other containers have a problem in treating 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, no biodegradable adhesive has been used for this biodegradable plastic container.

[0009]

The present invention was devised in order to solve such a problem.
An object of the invention is to provide a hot melt type adhesive having biodegradability.

The present invention relates to a biodegradable hot melt type adhesive comprising 100 parts by weight of raw rosin, 10 to 200 parts by weight of natural rubber, and 10 to 200 parts by weight of a plant or mineral wax.

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 hot melt 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.

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 wax used in the present invention is a plant wax or a mineral petroleum wax, and particularly, castor wax, carnauba wax No. 2, candelia, hardened soybean oil, rice wax, 180 ° C. microwax, paraffin wax, montan wax. Is. The wax is an ester of a fatty acid and a higher monohydric alcohol or a dihydric alcohol which is insoluble in water, and is different from fats and oils containing an ester of a fatty acid and glycerin as a main component. The plant wax is present on the epidermis of the plant to prevent its wetting and drying, and also has a heat insulating action. There are various kinds of mineral petroleum waxes, but paraffin wax and microcrystalline wax are generally used. The paraffin wax is mainly composed of a mixture of linear hydrocarbons called n-paraffins having 25 to 35 carbon atoms, which contains a large amount of isoparaffin and cycloparaffin, and the properties of the paraffin wax vary greatly depending on the mixing ratio. Paraffin has a relatively simple composition and therefore has no variety of properties, but microwax can be characterized by flexibility, adhesiveness, heat stability, and cold resistance.

Such a natural rubber-degrading bacterium is a bacterium that lives in general soil and is not a special bacterium. The degrading bacteria of natural rubber are Doi et al. (Japanese Patent Publication No. 63-5426, Journal of Japan Agricultural Science, 65, 981 (1991), Appl. Envir.
on. Microbiol. 50,965 (198
5)), it is known to belong to the genus Nocardia or the genus Rhodococcus. Further, the biodegradability of the wax used in the present invention is a bacterium that lives in general soil, and is not a special bacterium. The biodegradability of waxes has been reported in several papers (Oil Chemistry, 36, 46 (1987),
Oil Chemistry, 36, 852 (1987)).

In the present invention, as the filler, softening agent and antioxidant, 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. INDUSTRIAL APPLICABILITY The present invention is applied to hot melt type adhesives that require biodegradability.

The composition of raw rosin, natural rubber and wax is
Natural rubber 10 to 200 per 100 parts by weight of raw rosin
The wax is used in an amount of 20 to 150 parts by weight, preferably 10 to 2 per 100 parts by weight of raw rosin.
00 parts by weight, preferably 20 to 100 parts by weight. When the amount of natural rubber is 10 parts by weight or less with respect to 100 parts by weight of raw rosin, the holding power is lowered, and when it is 200 parts by weight or more, it does not melt even if heat is applied and it does not become a hot melt type adhesive. If the wax content is 10 parts by weight or less with respect to the raw rosin, the setting speed is slow, and if it is 200 parts by weight or more, the adhesive strength is reduced.

[0018]

EXAMPLES The 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.

[0019]

[Table 1]

Comparative Examples 1 to 6 As comparative examples, the raw rosin alone without the fungus (Comparative Example 1), the fungus only without the rosin (Comparative Example 2), the 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 indicates 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.

[0021]

[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.) A culture solution was prepared in the same manner as in Comparative Example 1 and added with 0.5 g of the above-mentioned natural rubber (sterilized with 70% 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

[0023]

[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 13 Biodegradable Samples of Wax Carter wax (vegetable wax) Carnauba No. 2 (vegetable wax) Candelia (vegetable wax) Soybean hydrogenated oil (vegetable wax) Paraffin wax (mineral petroleum wax) ) Montan wax (mineral-based petroleum wax) Rice wax (vegetable wax) Comparative Examples 7 to 8 As Comparative Example 7, the wax was not added, only the bacteria were added, and the polyethylene wax composed of the synthetic hydrocarbon (Comparative Example 8) and the bacteria were added. The same method was used. Measurement items A culture solution was prepared in the same manner as in Comparative Example 1, and the above waxes 0.
This was done by adding 5 g of powder. Regarding the presence or absence of biodegradability, the number of viable bacteria was measured after 3 months, and those showing growth were judged to be biodegradable. result

[0026]

[Table 4]

It can be seen that among the waxes, the number of bacteria in the culture liquid of plant wax and mineral petroleum wax is higher than that of the wax-free system. The fungus proliferated because it decomposed plant and mineral petroleum waxes and used them as a nutrient source.

Comparative Example 14 Natural rubber (pale crepe, masticated 10 times), Chinese rosin and biodegradable montan wax were heated and melt mixed to obtain a hot melt adhesive. The shear adhesive strength and the holding strength of the obtained hot melt adhesive were evaluated as follows, and Table 5 was obtained.

Shearing adhesive strength The obtained adhesive is melted and coated on one end of each aluminum plate having a length of 50 mm, a width of 10 mm and a thickness of 0.5 mm to adhere an aluminum plate of the same size. .
Then, the shear strength was measured at a pulling rate of 5 mm / min under the conditions of 25 ° C. and relative humidity of 65%.

Holding power The obtained hot-melt type adhesive agent is 25 mm in width and 50 in length.
mm, thickness 0.1 mm aluminum plate and vertical 25 mm,
Adhesion of 25 mm wide to a stainless steel plate (SUS304) polished with sandpaper # 280, load 1 kg
The distance (mm) at which the aluminum plate fell off the stainless steel plate was measured.

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 m × 100 mm sample (an aluminum plate with a hot melt adhesive thickness of 0.5 mm) was placed on the ground surface. 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 180 days, the sample was dug up, and the weight retention rate of the sample was examined by the formula (1). result

[0032]

[Table 5]

According to Examples 14 to 18, the adhesive strength is good,
The result was biodegradable.

Comparative Examples 9 to 11 As comparative examples, a hot melt adhesive composed of a synthetic material and a hot melt adhesive composed of a composition ratio of natural rubber, raw rosin and wax other than the above are shear adhesive strength, holding power and raw material. The degradability was shown in Comparative Examples 9-11.

[0035]

The hot melt adhesive of the present invention has biodegradability and excellent adhesive properties. Further, an adhesive whose treatment is regarded as a problem is used as an adhesive effective for environmental problems in which a solvent does not evaporate during use and is decomposed by microorganisms.

Claims (2)

[Claims] 1. 100 parts by weight of raw rosin and 10 to 10 parts of natural rubber
200 parts by weight and plant-based or mineral wax 10-2
A biodegradable hot melt type adhesive comprising 100 parts by weight. 2. The biodegradation according to claim 1, wherein the plant or animal wax is at least one selected from castor wax, carnauba wax, candelia wax, soybean hydrogenated oil, paraffin wax, montan wax and rice wax. Hot melt adhesive.