JPH1121533A - Resin for pressure-sensitive adhesive, resin composition for pressure-sensitive adhesive and pressure-sensitive adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin having biodegradability and showing good pressure-sensitive adhesiveness in a wide temperature range by selecting a resin comprising an aliphatic polyester having a specified or lower glass transition temperature. SOLUTION: This resin comprises a methyl-side-chain-containing aliphatic polyester represented by the formula and having a glass transition temperature of -40 deg.C or below. This is mixed with a tackifier, a filler, a plasticizer, etc., to obtain a resin composition. A solution prepared by dissolving this composition in a solvent is applied to a base film and dried to form a pressure-sensitive adhesive tape having a 10-1,000 μm thick pressure-sensitive adhesive layer. The thermoplastic polyester is obtained by effecting the preliminary esterification of a glycol such as propylene glycol with a dibasic acid such as adipic acid in the presence of a Ti catalyst and subjecting the product to a deglycolation reaction in a high vacuum at a constant acid value. In the formula, a and b are each an integer of 0-6, a+b=1-12; c is an integer of 4-12; and m is a degree of polymerization corresponding to a number-average molecular weight of 2,000-50,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive resin, a pressure-sensitive adhesive resin composition containing the same, and a pressure-sensitive adhesive tape. The present invention relates to a pressure-sensitive adhesive resin, a pressure-sensitive adhesive resin composition, and a pressure-sensitive adhesive tape exhibiting good pressure-sensitive adhesive performance even in a use environment.

[0002]

2. Description of the Related Art The emergence of various synthetic polymers since the middle of the 20th century has greatly contributed to making our lives comfortable and enriched, but on the other hand, they do not exist in nature and are difficult to decompose. The fact is that the waste is having a serious adverse effect on the global environment. Incidentally, it is said that the amount of plastic discharged annually in Japan alone exceeds 5 million tons, and the conventional treatment such as incineration and landfill has already caused serious and various problems. In other words, incineration causes new environmental pollution with the generation of carbon dioxide gas, and the land itself that allows landfill disposal is disappearing. Therefore, as the concern about global environmental issues is deepening internationally, there is a need for the development of a new plastic treatment method or a new material that is easily degradable after disposal.

[0003] Biodegradable plastics are completely decomposed into carbon dioxide, water, and the like by microorganisms in the soil or water, and are about to enter the stage of popularization under the name of "green plastic". Various materials are proposed by each company, for example, 3-hydroxybutyric acid-3-hydroxyvaleric acid copolymer synthesized by microorganisms, fatty acid polyester as a chemical synthesis system,
Polylactic acid, polyglycolic acid, polyvinyl alcohol,
And polymalic acid.

On the other hand, with the development of industry, the performance of the adhesive tape itself has been improved, and the field of use of the adhesive tape has rapidly expanded.
At present, it is widely used in various industrial fields such as agriculture, forestry, horticulture, hygiene, medical care, packaging, construction, industrial materials, electronic materials, and the like, and is playing a role as an industrial material.

[0005] In general, an adhesive tape is composed of a base film and an adhesive. The adhesive is mainly composed of a rubber-based elastic material such as natural rubber, polyisoprene, butyl rubber, and styrene-butadiene rubber, to which a tackifier is added, and a rubber-based adhesive, an acrylic acid ester polymer, and acetic acid. Acrylic adhesives which are copolymers with vinyl monomers such as vinyl, methacrylic acid ester, acrylic acid and methacrylic acid; plasticizers for vinyl polymers such as vinyl chloride / vinyl acetate copolymer and vinyl acetate polymer And a silicone-based pressure-sensitive adhesive composed of a rubber-like siloxane and a resin-like siloxane. Examples of the base film include papers such as Japanese paper and kraft paper, cloths such as cotton, fabric, synthetic fiber, and non-woven fabric, cellophane, polyethylene, polyester, polyvinyl chloride, acetate, polypropylene, polystyrene, polyvinylidene chloride, and polybutadiene. , Polyacrylonitrile and the like are appropriately selected and used depending on the application.

When natural cellulose and its derivatives are used as a base film or a pressure-sensitive adhesive, the properties such as water resistance are inferior and the quality control is difficult as the required performance from various industrial fields increases. Most of them tend to be replaced by plastic substrates having no properties. It has already been described that the pressure-sensitive adhesive tape using such a plastic substrate causes a serious problem in terms of environmental destruction upon disposal.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. Hei 4-220478 proposes an adhesive tape using a biodegradable base film, but a plastic material which does not biodegrade into an adhesive is used. Yes, there is still room for improvement. For example, Japanese Patent Application Laid-Open No. Hei 6-228508 discloses an adhesive tape using a biodegradable linear aliphatic polyester. Is not enough,
For example, in winter, the performance is remarkably deteriorated, which is insufficient for practical use.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have solved the above-mentioned conventional problems, have shown the biodegradability of the adhesive tape as a whole, and have good adhesive performance even under various use environments. It is an object of the present invention to industrially provide the pressure-sensitive adhesive resin, the pressure-sensitive adhesive resin composition, and the pressure-sensitive adhesive tape described above.

[0009]

Means for Solving the Problems The present inventors focused on aliphatic polyesters which are the most excellent in biodegradability among chemical synthetic plastics and whose physical properties are relatively easy to design. A series of enormous trial productions and tests on biodegradability were conducted. As a result, it has been confirmed that the polyester having a specific molecular structure has a target biodegradability and sufficient adhesiveness, and particularly exhibits adhesiveness that can withstand practical use in a wide temperature range including a low temperature region. It was completed.

That is, the present invention provides a pressure-sensitive adhesive resin comprising an aliphatic polyester having a repeating unit represented by the following chemical formula (1) and having a Tg of -40 ° C or lower.

[0011]

Embedded image

Wherein a and b are each an integer of 0 to 6, a + b is an integer of 1 to 12, and c is 4 to
An integer of 12 and m is a number average molecular weight of 2,000 to 5
(Represents the degree of polymerization equivalent to 0000)

The present invention also provides a pressure-sensitive adhesive resin composition comprising the pressure-sensitive adhesive resin and other additives.

The present invention further provides a pressure-sensitive adhesive tape obtained by coating at least one surface of a biodegradable substrate film with the resin for pressure-sensitive adhesive or the resin composition for pressure-sensitive adhesive.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION
It is made of the aliphatic polyester represented by the chemical formula (1), and has one feature in that it has a methyl group in a side chain. This can be easily synthesized by a known esterification reaction between dibasic acid and glycol. It can also be synthesized by a transesterification reaction between dimethyl ester of dibasic acid and glycol, which produces methanol as a by-product.

In the above formula (1), a and b
Is an integer of 0 to 6, preferably 1 to 2,
a + b is an integer of 1 to 12, preferably 2 to 4, c
Is an integer of 4 to 12, preferably 4 to 8, and m represents a degree of polymerization corresponding to a number average molecular weight of 2,000 to 50,000.

The number average molecular weight of the aliphatic polyester of the pressure-sensitive adhesive resin of the present invention is preferably from 2,000 to 50,000,
Desirably, it is 5,000 to 30,000. When the number average molecular weight of the pressure-sensitive adhesive resin of the present invention is within these ranges, the pressure-sensitive adhesive performance and heat resistance aimed at by the present invention are further improved.

When the aliphatic polyester of the pressure-sensitive adhesive resin of the present invention has a number average molecular weight of 5,000 or more, some contrivance is required in the esterification reaction. For example, when the glycol component is in a small excess, an initial esterification reaction is performed using a titanium-based catalyst such as tetraalkyltitanium, and when the acid value falls below a certain value, for example, when the acid value falls below 10 And a deglycol reaction is performed under a high vacuum condition of about 1 Torr. According to this method, the number average molecular weight can be made much larger, for example, about 30,000, and performance improvements such as strength, durability, and water resistance can be seen.

In the present invention, the following can be exemplified as the glycol for constituting the aliphatic polyester represented by the chemical formula (1). Propylene glycol, 2-methyl-1,3-propanediol, 1-methyl-1,3
-Propanediol, 3-methyl-1,5-pentanediol, 4-methyl-1,7-heptanediol, 2-
Methyl-1,6-hexanediol, 3-methyl-1,
6-hexanediol, 1-methyl-1,6-hexanediol, 4-methyl-1,9-nonanediol, 2-
Methyl-1,9-nonanediol, 3-methyl-1,9
-Nonanediol.

In the present invention, it is possible to use the following polymethylene glycol in combination with a part of the above-mentioned glycols. Ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol. However, in that case, the molar ratio of polymethylene glycol not contributing to the methyl group side chain to the total number of moles of glycol must not exceed 40%.
When the molar ratio of polymethylene glycol exceeds 40%, the cohesive force between molecules increases, Tg increases, and the performance of a pressure-sensitive adhesive using this as a main component at a low temperature tends to decrease. The preferred range is 0 to
20 mol% is good.

In the present invention, the following can be exemplified as the dibasic acid for constituting the aliphatic polyester represented by the chemical formula (1). Adipic acid, azelaic acid, sebacic acid, dodecanedioic acid.

The Tg in the present invention can be easily calculated by a generally performed DSC measurement.
The Tg of the pressure-sensitive adhesive resin of the present invention is preferably −40 ° C. or lower, and more preferably −60 ° C. or lower. When the Tg exceeds -40 ° C, not only does the peel strength of the adhesive become adversely affected, but also the performance at low temperatures becomes inferior.

The resin for pressure-sensitive adhesive of the present invention can be used in combination with various additives as long as the biodegradability is not impaired, to form a resin composition for pressure-sensitive adhesive. The following can be illustrated as these additives. Natural resins such as rosin and dammar, modified rosin, derivatives of rosin and modified rosin, polyterpene resins, terpene modified products, aliphatic hydrocarbon resins, cyclopentadiene resins, aromatic petroleum resins, phenolic resins, alkylphenol-acetylene -Based resin, styrene-based resin, coumarone indene resin, xylene resin, tackifiers such as vinyl toluene-α-methylstyrene copolymer, phthalic acid-based plasticizer, phosphate ester-based plasticizer, adipate-based plasticizer, Sebacate plasticizer, ricinoleate plasticizer, polyester plasticizer, epoxy plasticizer, plasticizer such as chlorinated paraffin, or clay, titanium oxide,
Fillers such as calcium carbonate, other softeners, antioxidants, stabilizers, fungicides, thickeners, coloring agents, defoamers, and adhesion improvers. These additives are suitably used in an amount of about 5 to 50% by weight based on the whole resin composition for an adhesive.

The base film constituting the pressure-sensitive adhesive tape by applying the pressure-sensitive adhesive resin or the pressure-sensitive adhesive resin composition of the present invention includes paper such as Japanese paper and kraft paper, cotton, cloth, synthetic fiber, and nonwoven fabric. Cloth, cellophane, polyethylene, polyester, polyvinyl chloride, acetate, polypropylene, polystyrene, polyvinylidene chloride, polybutadiene, polyacrylonitrile and the like can be appropriately selected and used according to the intended use. In order to make use of the biodegradation characteristics of the resin, it is preferable to use a biodegradable base film. For example, the following can be exemplified. Polyester produced by microorganisms: 3-hydroxybutyric acid
Polysaccharides such as 3-hydroxyvaleric acid copolymer, microfibril cellulose and burlan; Chemical synthesis system: polybutylene succinate, polybutylene succinate adipate, polyethylene succinate,
Glycols such as polyethylene succinate adipate
Aliphatic dicarboxylic acid copolymer, polylactic acid, polycaprolactone, poly-γ-methylglutamate, thermoplastic polyvinyl alcohol. Natural polymer system: starch + modified polyvinyl alcohol, starch + natural resin, chitosan + cellulose. Moreover, you may comprise a base film by compounding said material.

In the present invention, in order to form a pressure-sensitive adhesive tape by combining a base film and a resin or composition for a pressure-sensitive adhesive,
For example, it can be implemented as follows. The pressure-sensitive adhesive resin or composition is dissolved in a suitable solvent, a pressure-sensitive adhesive layer is provided on one or both sides of the base film, and dried. If necessary, a release paper layer may be further provided on the surface of the pressure-sensitive adhesive layer. In addition, as a method for producing the above-mentioned pressure-sensitive adhesive tape, a conventionally known production apparatus can be used without any change. The thickness of the pressure-sensitive adhesive layer after drying is preferably, for example, about 10 to 1000 μm.

The method of using the pressure-sensitive adhesive tape of the present invention includes:
Although not particularly limited, agriculture, forestry and fisheries, horticulture, sanitation,
It can be particularly suitably used in the fields of packaging, medical treatment and the like.

To confirm the biodegradability of the pressure-sensitive adhesive resin, composition or pressure-sensitive adhesive tape of the present invention, the specimen is kept in soil or water containing activated sludge for a certain period, and the progress of weight loss is quantitatively grasped. Can be easily implemented. Alternatively, evaluation can also be made by integrating the amount of generated gas. As an even simpler method, a film made of a material having known biodegradability is subjected to a biodegradation test by sandwiching the film of the pressure-sensitive adhesive resin or composition of the present invention from both sides and subjecting the film to known biodegradability. With the disappearance of the film comprising the material, it can be concluded that the pressure-sensitive adhesive resin or composition is also biodegradable.

[0028]

The present inventors believe that the reason why the pressure-sensitive adhesive resin or composition of the present invention has biodegradability and exhibits good pressure-sensitive adhesive properties even in a low-temperature region is as follows. . That the glycol component of the aliphatic polyester having a side chain methyl group was selectively used, and a compound having a polymethylene unit having a fixed length or more in a saturated dibasic acid was selected, and both were complexed. It is thought that Tg is reduced by this, and good performance can be maintained even in a low temperature region.

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which by no means limit the present invention. [Synthesis of Polyester (A-1)] Thermometer, stirrer,
4-methyl-1,7-heptanediol was placed in a 2-liter flask equipped with a distillation condenser and a gas introduction tube.
584 g (4.20 mol), 808 g of sebacic acid (4.
0 mol) and 0.70 g of tetraisopropyl titanate, and an esterification reaction was carried out at 150 to 220 ° C. Next, the temperature was lowered to 190 ° C., and 0.35 g of phosphorous acid was added.
The pressure was initially reduced at 190 to 200 ° C. to 7 to 10 Torr, and finally to 5 Torr. After the reaction for 8 hours, the resin in the flask was poured into a metal vat and solidified by cooling. The obtained resin was pale yellow, and had a number average molecular weight of 5,300, a weight average molecular weight of 12,800, and a DSC measured by GPC.
The measured Tg was -71 ° C. This resin (A-
1).

[Synthesis of Polyester (A-2)] In a 2-liter flask equipped with a thermometer, a stirrer, a distillation condenser, and a gas inlet tube, 378 g of 3-methyl-1,5-pentanediol (3. 2 mol), ethylene glycol 62 g (1.0 mol), dodecane diacid 920 g
(4.0 mol), tetraisopropyl titanate 0.7
0 g was added, and an esterification reaction was performed at 145 to 180 ° C. Next, 0.35 g of phosphorous acid was added, and 190-200 ° C.
The pressure was initially reduced to 7 to 10 Torr, and finally to 5 Torr. After the reaction for 6 hours, the resin in the flask was poured into a metal vat and solidified by cooling. The obtained resin was pale yellow, had a number average molecular weight of 6,100, a weight average molecular weight of 14,300, and a Tg of -55 ° C by DSC measurement, as measured by GPC. This resin is designated as (A-2).

[Synthesis of Polyester (A-3)] In a 2-liter flask equipped with a thermometer, a stirrer, a fractionating condenser, and a gas inlet tube, 142 g of 3-methyl-1,5-pentanediol (1. 2 mol), 186 g (3.0 mol) of ethylene glycol, 920 g of dodecane diacid
(4.0 mol), tetraisopropyl titanate 0.6
70 g was added, and an esterification reaction was performed at 145 to 180 ° C. Next, 0.3 g of phosphorous acid was added, and the pressure was reduced at 190 to 200 ° C. to 7 to 10 Torr initially, and finally to 4 Torr. After the reaction for 6 hours, the resin in the flask was poured into a metal vat and solidified by cooling. The obtained resin was pale yellow, had a number average molecular weight of 5,200 and a weight average molecular weight of 13,800 as measured by GPC, and had a Tg of −35 ° C. as measured by DSC. This resin is designated as (A-3).

Example 1 (A-1) 500 parts by weight of a resin were weighed into a flask, and 25 parts by weight of rosin and 1 part of toluene
After adding 50 parts by weight and stirring and mixing well, apply to one side of a polylactic acid film (thickness of 100 μm, Ecopla, manufactured by Cargill Co., Ltd.) so that the film thickness after drying becomes 100 μm, and dry. An adhesive tape was made. The pressure-sensitive adhesive tape thus obtained was subjected to JIS K-6911
A test for peel strength was performed in accordance with. The result is 1.7kg
/ Inch and the peel strength of a commercially available cellophane pressure-sensitive adhesive tape were 1.6 kg / inch. When the adhesive tape stored in the refrigerator (-5 ° C.) was adhered to the adherend placed in the refrigerator, and the peel strength was measured in the same manner, a reasonable strength of 0.5 kg / inch was obtained. Was done.

(Comparative Example 1) A trial production of a pressure-sensitive adhesive tape was performed by the same operation and prescription as in Example 1 except that the resin (A-3) was used. However, when this tape was subjected to a low-temperature adhesion test using the same refrigerator as in Example 1, it was found that the tape did not show any adhesion.

Example 2 (A-2) Polybutylene succinate film (bionole, thickness 100 μm, manufactured by Showa Polymer Co., Ltd.) as a substrate film using resin
A trial production of an adhesive tape was performed by the same operation and prescription as in Example 1 except that the adhesive tape was used. This product was confirmed to have good adhesiveness equivalent to that of Example 1. Next, two test pieces each having a length of 15 cm and having a length of 15 cm were laminated in layers, and the culture soil (Kawasuna:
(Bark: oil residue = 90: 5: 5) and left at 35 ° C. After 4 months, they all decompose and cannot be recovered.
It was confirmed that it was completely biodegraded.

[0035]

According to the present invention, a pressure-sensitive adhesive resin, a pressure-sensitive adhesive resin composition, and a pressure-sensitive adhesive tape exhibiting biodegradability as a whole and exhibiting good adhesive performance even under various use environments. Tape is provided.

Claims (3)

[Claims] 1. A pressure-sensitive adhesive resin comprising an aliphatic polyester having a repeating unit represented by the following chemical formula (1) and having a Tg of -40 ° C. or lower. Embedded image (In the formula, a and b are each an integer of 0 to 6,
a + b is an integer of 1 to 12, c is an integer of 4 to 12, and m represents a degree of polymerization corresponding to a number average molecular weight of 2,000 to 50,000. 2. A resin composition for a pressure-sensitive adhesive, comprising the resin for a pressure-sensitive adhesive according to claim 1 and other additives. 3. A pressure-sensitive adhesive tape obtained by coating at least one surface of a biodegradable substrate film with the pressure-sensitive adhesive resin according to claim 1 or the pressure-sensitive adhesive resin composition according to claim 2.