JP2674792B2 - Adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid polymer post-crosslinking pressure-sensitive adhesive composition having excellent heat aging resistance and weather resistance.

(Prior Art) Conventionally, solid rubber such as natural rubber has been used as an adhesive. In recent years, from the viewpoints of resource saving, energy saving, improvement of productivity, etc., attempts have been made to prepare an adhesive by a method of post-crosslinking a low molecular weight liquid polymer with a crosslinking agent. Compared with the method using solid rubber, the method using this liquid polymer does not require steps such as mastication, cutting, and dissolution of rubber, and since there is no need to use a solvent, its drying and recovery There are many advantages such as time saving and energy saving, no equipment, simple equipment, and significantly high production speed.
As a method for obtaining an adhesive with this liquid rubber, a method using a low molecular weight polyisoprene having a hydroxyl group introduced into its side chain (JP-A-57-47368), a method using a polybutadiene having hydroxyl groups at both ends (JP-A-62-263275
Is known. These methods have achieved their objectives in terms of energy saving and improvement of productivity, and the performance as a pressure-sensitive adhesive is tentatively satisfactory in a normal state. However, the environment in which the pressure-sensitive adhesive is used has become severer year by year, and in addition to the above characteristics, higher performance such as heat aging resistance and weather resistance has been required. Conventional adhesives based on diene rubber have been unable to meet this purpose.

(Problems to be Solved by the Invention) An object of the present invention is to obtain a pressure-sensitive adhesive which is solvent-free, has excellent heat aging resistance and weather resistance, and has sufficient adhesion performance, using a liquid polymer as a raw material.

(Means for Solving the Problems) According to the present invention, the above object is achieved by a pressure-sensitive adhesive composition containing a specific hydroxyl group-containing liquid hydrogenated polyisoprene. That is, the present invention provides (a) a carbon-carbon double bond in the molecular chain of a hydroxyl group-containing liquid polyisoprene having a molecular weight of 700 to 7,000, a vinyl bond amount of 20 mol% or less, and 1.5 or more hydroxyl groups per molecule. Hydroxyl group-containing hydrogenated liquid polyisoprene obtained by hydrogenating 40% or more, (b) Addition ratio of 0.05 to 100 parts by weight of the hydroxyl group-containing hydrogenated liquid polyisoprene
To 5 parts by weight of a compound having 2 to 4 phenol residues, and (c) the hydroxyl group-containing hydrogenated liquid polyisoprene has a molar ratio of isocyanate groups to hydroxyl groups of 0.
It relates to a pressure-sensitive adhesive composition comprising an amount of polyisocyanate compound of 5 to 4.

The vinyl bond amount (1,2 or 3,4 bond amount) of the hydroxyl group-containing liquid polyisoprene must be 20% mol or less. If the vinyl bond content exceeds 20 mol%, the mechanical properties such as rubber elasticity of the polyurethane at low temperatures are deteriorated. The microstructures such as 1,4-cis, 1,4-trans, 1,2-vinyl and 3,4-vinyl are based on the values obtained from ¹ H-NMR spectrum.

The number average molecular weight of the hydroxyl group-containing liquid polyisoprene is
It must be between 700 and 7,000. Number average molecular weight is 70
If it is less than 0, the cured product with the polyisocyanate compound does not have good rubber elasticity. On the other hand, when it exceeds 7,000, the liquid polyisoprene containing hydroxyl group does not show good fluidity. Further, the hydroxylated hydrogenated polyisoprene obtained by hydrogenating this does not show fluidity either. The number average molecular weight of the hydroxyl group-containing liquid polyisoprene is preferably 1,000 to
5,000.

The number of hydroxyl groups (= average number of hydroxyl groups per molecule) of the hydroxyl group-containing liquid polyisoprene needs to be 1.5 to 4. If the number of hydroxyl groups is less than 1.5, sufficient cross-linking cannot be obtained in the reaction with the polyisocyanate compound, resulting in problems such as poor mechanical strength of polyurethane. If the number of hydroxyl groups exceeds 4, the crosslinking density will be too high and the cured product will not exhibit good rubber elasticity. Therefore, the number of hydroxyl groups needs to be in the above range, and is preferably 1.8 to 3.

The hydroxyl group may be at the end of the molecular chain of the hydroxyl group-containing liquid polyisoprene or in the chain, but is preferably at both ends.

Such a hydroxyl group-containing liquid polyisoprene is known or can be easily produced by a known method. For example, isoprene monomer is hydrogen peroxide, an azo compound having a hydroxyl group (for example, 2,2'-azobis [2-methyl-N
-(2-hydroxyethyl) propionamide] or the like) or a peroxide having a hydroxyl group (for example, cyclohexanone peroxide or the like) as a polymerization initiator to obtain a hydroxyl group-containing liquid polyisoprene. The amount of the polymerization initiator used is, for example, H ₂ O ₂ 1.2 to 12 g, 2,2′-azobis- [2-methyl-N- (2-hydroxyethyl) -propionamide] 9.2 to 92 g, relative to 100 g of the isoprene monomer. Cyclohexanone peroxide 7.6-7
6g is suitable. The polymerization can be carried out without a solvent, but it is preferable to use a solvent because of easy control of the reaction. As the solvent, ethanol, isopropanol and the like are usually used. The reaction temperature is suitably 100 to 150 ° C, and the reaction time is suitably 5 to 15 hours.

Alternatively, a hydroxyl group-containing liquid polyisoprene can be obtained by producing an isoprene living polymer by anionically polymerizing an isoprene monomer using a catalyst such as naphthalenedilithium, and further reacting a monoepoxy compound or the like. The polymerization can be carried out without a solvent, but it is preferable to use a solvent from the same viewpoint as in the case of radical polymerization. As the solvent, a saturated hydrocarbon such as hexane and cyclohexane is used. Reaction temperature is 50-100
The reaction time is 1 to 10 hours. In some cases, liquid polyisoprene having a hydroxyl group introduced by the side chain addition reaction can be used (for example, JP-A-57-1600).
No. 3).

In the present invention, the hydroxyl group-containing liquid polyisoprene is hydrogenated by a known method using a homogeneous catalyst, a heterogeneous catalyst or the like. At this time, 40% or more of the carbon-carbon double bonds in the hydroxyl group-containing liquid polyisoprene are hydrogenated.

When the hydrogenation rate is less than 40%, deterioration of heat resistance and light resistance due to heat or light due to the double bond of the cured product with the polyisocyanate compound becomes a problem. The hydrogenation rate is preferably 60
% Or more, more preferably 80% or more.

When using a homogeneous catalyst for hydrogenation, saturated hydrocarbons such as hexane and cyclohexane, benzene, toluene,
Use aromatic hydrocarbons such as xylene as a solvent at room temperature to 150
The hydrogenation reaction is carried out at a reaction temperature of ° C and a hydrogen pressure of atmospheric pressure to 50 kg / cm ² . As a homogeneous catalyst, use a Ziegler catalyst, which is a combination of a transition metal halide and an alkyl compound such as aluminum, an alkaline earth metal or an alkali metal, in an amount of about 0.01 to 0.1 mol% per carbon-carbon double bond of a hydroxyl group-containing liquid polyisoprene. To do. Reaction usually 1-24
End in time.

When using a heterogeneous catalyst for hydrogenation, hexane,
Saturated hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, diethyl ether,
Tetrahydrofuran (THF), ethers such as dioxane, alcohols such as ethanol, isopropanol, etc., or a mixed system of these are used as a solvent, and hydrogenation is carried out at a reaction temperature of room temperature to 200 ° C. under a hydrogen pressure of atmospheric pressure to 100 kg / cm ^2. The reaction is carried out.

As the heterogeneous catalyst, a catalyst such as nickel, cobalt, palladium, platinum, rhodium, or ruthenium is used alone or supported on a carrier such as silica, diatomaceous earth, alumina or activated carbon, and the amount used is 0.5 with respect to the polymer weight. ~Ten
% By weight is appropriate. The reaction is usually completed in 1 to 48 hours.

In the present invention, the compound having 2 to 4 phenol residues is used as an antioxidant and is added in an amount of 0.05 to 5 parts by weight with respect to 100 parts by weight of the hydroxylated hydrogenated liquid polyisoprene. Examples of such compounds include 2,2 '
-Methylene-bis- (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis (4-ethyl-6)
-Tert-butylphenol), 4,4'-methylene-bis- (2,6-di-tert-butylphenol), 2,2'-methylene-bis- (6-α-methylbenzine-p-cresol), etc. Bisphenol compounds, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 1,1,3-tris- (2-methyl- Trisphenol compounds such as 4-hydroxy-5-tert-butylphenyl) butane, tetrakis- [methylene-3- (3,5'-di-tert-butyl-4'-hydroxyphenyl) propionate] methane, etc. Examples thereof include phenolic compounds. Monophenolic compounds which have hitherto been most frequently used as phenolic antioxidants are completely unsuitable for the purpose of the present invention. Amine-based compounds, which are other types of antioxidants, also cause discoloration,
There is a big problem of contamination, which is not suitable for the purpose of the present invention. When the addition amount of the compound having 2 to 4 phenol residues is less than 0.05 parts by weight, the heat resistance improving effect cannot be obtained, and when the addition amount exceeds 5 parts by weight, the addition amount is less than that. If so, the effect is hardly changed, and the economic efficiency is rather deteriorated, which is not preferable.

The composition of the present invention contains the hydrogenated group-containing hydrogenated liquid polyisoprene obtained as described above and a polyisocyanate compound. The content ratio of both is the molar ratio of isocyanate group to hydroxyl group in polyisoprene, that is, NCO / OH
Is in the range of 0.5 to 4. When this ratio is less than 0.5, the crosslink density of the obtained pressure sensitive adhesive is too low and the cohesive force is too low, and when it exceeds 4, the crosslink density is too high and the pressure sensitive adhesive becomes poor. In all cases, a pressure-sensitive adhesive composition having sufficient performance cannot be obtained, which is not preferable.

Here, the polyisocyanate compound is not limited to obtainable,
An isocyanate compound containing two or more isocyanate groups in one molecule is used. Examples include tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, modified diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and the like.

The pressure-sensitive adhesive composition of the present invention may contain a tackifying resin. Typical examples of tackifying resins include terpene resins, terpene phenol resins, rosin resins, aromatic hydrocarbon petroleum resins, alicyclic hydrocarbon petroleum resins,
Examples thereof include aliphatic hydrocarbon petroleum resin, coumarone indene resin, and phenolic resin. These tackifying resins may be used alone or in combination of two or more. The amount of hydrogenated liquid isoprene containing hydroxyl groups
It is in the range of 5 to 250 parts by weight, preferably 20 to 60 parts by weight, relative to 100 parts by weight. If the amount used is too small, a pressure-sensitive adhesive composition having sufficient tackiness and adhesiveness cannot be obtained, while if too large, a pressure-sensitive adhesive composition having sufficient cohesive force cannot be obtained.

The pressure-sensitive adhesive composition of the present invention may further contain other additives such as an ultraviolet absorber; a pigment; a softening agent such as process oil, etc., if necessary.

The pressure-sensitive adhesive composition of the present invention is used by coating it on a substrate such as paper, cellophane, polyester, etc. and crosslinking it by heating.
The temperature required for crosslinking is room temperature to 200 ° C., and the reaction time required for crosslinking is 0.1 hour to 50 hours. However, in view of productivity, it is desirable to shorten the reaction time, and it is preferable to carry out the reaction at a temperature in the range of 80 to 150 ° C.

The pressure-sensitive adhesive composition of the present invention, paper, cloth, polypropylene,
Adhesive tape coated with a film of plastics such as polyester and vinyl chloride into a tape or sheet,
It can be used as an adhesive label or an adhesive sheet.

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Reference Example 1 60 mmol of m-divinylbenzene was dissolved in hexane, cooled to -10 ° C, and 130 mmol of n-BuLi was appropriately added to m-.
Dilithiohexylbenzene was produced, to which 2.2 mol of isoprene monomer was added and polymerized at 40 ° C. Then, 4 mol of ethylene oxide was added to the reaction system and the resulting product was poured into a large amount of methanol to obtain a liquid polyisoprene having hydroxyl groups at both ends as a precipitate. The hydroxyl group-containing liquid polyisoprene thus obtained had a molecular weight of 2900 and a vinyl bond content of 11
The number of mol% in one molecule was 1.92.

The obtained hydroxyl group-containing liquid polyisoprene was dissolved in dioxane, and then hydrogenated with Ru-C (Ru 5%) as a catalyst at a hydrogen pressure of 30 kg / cm ² . The catalyst was separated by passing after the reaction, and further vacuum dried to obtain a hydroxylated hydrogenated liquid polyisoprene (1). The hydrogenation rate measured by iodine value was 85%.

Examples 1 to 4 and Comparative Examples 1 to 4 Using the hydroxylated hydrogenated liquid polyisoprene (I) obtained in Reference Example 1 and various antioxidants, pressure-sensitive adhesive compositions were prepared according to the formulations shown in Table 1. The heat resistance was evaluated by preparing and measuring the adhesive performance, and at the same time, examining the performance change when heated in an 80 ° C. oven. Table-Results
It is shown in FIG.

Reference Example 2 An isoprene monomer was polymerized in the same manner as in Reference Example 1 except that m-divinylbenzene was 40 mmol and n-BuLi was 90 mmol, and the molecular weight was 3950 and the vinyl bond content was 10.5 mol%.
A hydroxyl group-containing liquid polyisoprene having 1.94 hydroxyl groups in the molecule was obtained. The obtained hydroxyl group-containing liquid polyisoprene was hydrogenated in the same manner as in Reference Example 1 to obtain a hydroxyl group-containing hydrogenated liquid polyisoprene (II). The hydrogenation rate at this time was 70%.

Examples 5-7 and Comparative Examples 5-7 Hydroxyl group-containing hydrogenated liquid polyisoprene (II) obtained in Reference Example 2 and tetrakis- [methylene-3- (3 ',
5'-di-tert-butyl-4'-hydroxyphenylpropionate] methane was used to prepare an adhesive composition according to the formulation shown in Table 3, and its adhesive performance and heat aging resistance were compared with those of Example 1. It evaluated similarly. The results are shown in Table-3.

(Effects of the Invention) The present invention provides a pressure-sensitive adhesive composition having excellent heat aging resistance and weather resistance, and having sufficient adhesive performance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naotake Minano 36 Towada, Kamisu-cho, Kashima-gun, Ibaraki Prefecture Kuraray Co., Ltd. Examiner Seiji Sakano (56) Reference JP-A-63-57626 (JP, A) Kosho 52-20518 (JP, B1)

Claims (1)

(57) [Claims] 1. A molecular weight of 700 to 7,000 and a vinyl bond amount of 20.
A hydroxyl group-containing hydrogenated liquid polyisoprene obtained by hydrogenating 40% or more of carbon-carbon double bonds in the molecular chain of a hydroxyl group-containing liquid polyisoprene having not more than mol% and 1.5 or more hydroxyl groups per molecule; ) A compound having 2 to 4 phenol residues in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of the hydroxyl group-containing hydrogenated liquid polyisoprene, and (c) in the hydroxyl group-containing hydrogenated liquid polyisoprene. A pressure-sensitive adhesive composition comprising a polyisocyanate compound in an amount such that the molar ratio of isocyanate group to hydroxyl group is 0.5 to 4.