JPS61145268A - Moisture-curing self-adhesive composition - Google Patents

Abstract

PURPOSE:To provide a moisture-curing self-adhesive compsn. having excellent storability and self-adhesiveness and high bonding strength, prepared by blending a specified polymer having an isocyanater group in its side chain, with an isocyanater group-contg. tackifier. CONSTITUTION:The self-adhesive compsn. consists of (1) a polymer having an isocyanate group in its side chain obtained by reacting 30mol% (meth) acryloyl troup-contg. unsatd. isocyanate with 70-99mol% monomer copolymerizable with the unsatd. isocyanate and (2) an isocyanate group-contg. tackifier. Preferred monomers for (1) are those which form a polymer with a glass transition point of below 30 deg.C. The polymer having an isocyanate group in its side chain is usually prepared by solution polymerization of (1) and (2).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a moisture-curing adhesive composition that cures by absorbing moisture in the air and is useful as an adhesive for a moisture-curing adhesive tape layer.

[Conventional technology]

In order to make adhesive tape into a hardening type, various proposals have been made for adhesives, but an adhesive tape that uses a slight epoxy adhesive and is heated and cured over a long period of time has been put into practical use. Adhesive tapes using adhesives that harden within a relatively short time at room temperature have not appeared on the market.

There are various methods for curing adhesives that harden at room temperature (for example, anaerobic curing methods and light curing methods).
Moisture-curing adhesives are considered to be the most convenient to use because they can be safely stored for long periods of time by eliminating the influence of moisture during storage, and if they harden after use, they can be attached to any object. .

The most typical moisture-curable polymer or oligomer is a so-called one-component type polymer having an isocyanate group at the end of the molecule. i? Solvent solutions of riethers and polyesters are known and are used as paints and adhesives.

Furthermore, in order to increase the adhesive strength of adhesive tapes, conventional adhesives have been modified with polyvalent incyana-1.

[Problem that the invention seeks to solve]

However, these conventional polymers and oligomers having isocyanate groups do not necessarily have sufficient storage stability due to the reactivity of the isocyanate groups, especially when attempting to cure adhesive tapes with moisture in the air. When the isocyanate or boot group is included in a polymer or olicomer, the moon with this isocyanate group? If moisture is absorbed during the process of applying the remer or oligomer to the base material and removing the solvent, the adhesive tape has a disadvantage in that its shelf life is significantly impaired and its commercial value is completely lost.

In addition, in the production process of the adhesive tape, it is a practical matter to use a moisture-curing type when the content of isocyanate groups is such that it is not affected in practical terms.

Complete drying of the entire manufacturing process is expensive, if not impossible, and undesirable.

The present inventors have an incyana-1 group in the molecule,
Isocyanatoethyl methacrylate from The Dow Chemical Company was used as one of the monomer components, along with other monomers such as butyl acrylate.

An attempt was made to produce a polymer having an isocyanate group in the side chain by solution copolymerizing 2-ethylhexyl acrylate (2-ethylhexyl acrylate, etc.), and found that it was easy to synthesize a copolymer if a sufficiently dehydrated solvent was used. Furthermore, it has been found that if the isocyanate group is at least 20 molar proportion of the total monomers, a moisture-curable adhesive polymer can be obtained.

However, this copolymer is unstable and has the disadvantage that it gels in about a week even in a system in which a moisture absorbent such as molecular sieve is added. In addition, the moisture-curing adhesive tape obtained by applying the Incyaner I group-containing copolymer to the base film immediately after production, obtained by the above method, is placed in a moisture-proof bag made from a laminate film of aluminum and polyethylene, and then placed inside a moisture-proof bag made from a laminate film of aluminum and polyethylene. Even if it was sealed together with an adhesive, it lost its stickiness the next day and could not function as an adhesive at all.

From this point of view, the present inventors conducted various studies in order to obtain a more stable moisture-curing adhesive tape, and as a result, the present inventors developed an unsaturated isocyanate having an acryloyl group or a methacryloyl group and a copolymer with the unsaturated isocyanate. If a mixture of available monomers is applied to a base material and then irradiated with active energy rays in the absence of air to form a polymer on the base material, it will be less affected by humidity during the production of adhesive tapes. I came to know that it has sufficient storage stability after being made into adhesive tape.

This method was a useful method for producing moisture-curable adhesive tapes, provided there was an apparatus for irradiating active energy rays.

However, this cannot be applied in cases where a device for irradiating active energy rays is not available, and therefore, there may be a need for a moisture-curable adhesive composition that can be applied to commonly used coating devices.

The isocyanate group of the side chain of a general dipolymer can be stored safely for a total of 100 moles of unsaturated isocyanate and monomers copolymerizable with the unsaturated isocyanate. As a curable type, the curability and physical properties after curing are insufficient.

[Means for solving problems]

However, as a result of further research, the present inventors found that in order to obtain a practical moisture-curing adhesive, there is a standard amount of isocyanate groups p per unit weight; It does not depend solely on the isocyanate groups of the polymer, but can be preserved as long as the composition has sufficient isocyanate groups for moisture curing by using an isocyanate group-containing tackifier in combination with an isocyanate group-containing polymer. The present invention was completed based on the knowledge that a moisture-curable pressure-sensitive adhesive composition with excellent properties, adhesiveness, and adhesive strength can be obtained.

That is, the present invention provides (1) (a) an unsaturated isocyanate having an acryloyl group or a methacryloyl group;
The present invention relates to a moisture-curable adhesive composition comprising a polymer having an isocyanate group in its side chain obtained by reacting the polymer with molti, and (2) a tackifier having an isocyanate group.

As the unsaturated isocyanate having an acryloyl group or a methacryloyl group (hereinafter abbreviated as (meth)acryloyl group) used in the present invention, "Isocyanate ethyl methacrylate" 7 horse CH2 commercially available from Dow Chemical Company is used. =C-C-0-CH2-CH2-NCO is useful.

In addition, a reaction product of a diisocyanate and an unsaturated monoalcohol having a (meth)acryloyl group in which the molar ratio of isocyanate groups to hydroxyl groups is substantially 161 can also be used.

Examples of diisocyanates include 2,4-1-lylene cyanate, 2,4. - ) mixture of lylene diisocyanate and 2.6-) lylene diisocyanate, paraphenylene diisocyanate, 1,5-naphthylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate Examples thereof include hydrogenated xylylene diisocyanate, 1°6-hexamethylene diisocyanate, isophorone diisoneanate, and the like.

Examples of unsaturated monoalcohols for introducing (meth)acryloyl groups by reacting with these diisocyana-1. -Hydroxypropyl methacrylate and the like.

In addition to these unsaturated monoalcohols having (meth)acryloyl groups, reaction products of monoepoxy compounds and acrylic acid or methacrylic acid can also be used, examples of which include phenylglycyl ether,
Examples include reaction products of butyl glycidyl ether, octyl glycidyl ether or styrene oxide and acrylic acid or methacrylic acid.

An example of a reaction product between phenyl glycidyl ether and acrylic acid is shown by the following formula.

When reacting a diisocyanate with an unsaturated monoalcohol, it is advantageous to use an organic tin compound or a tertiary amine compound, which is usually used as a urethanization catalyst, to prevent 1 reaction during the reaction. It is preferable to include a one-coat inhibitor commonly used in

For example, when 2.4-)lylene diisocyanate is used as the diisocyanate and 2-hydroxyethyl acrylate is used as the unsaturated monoalcohol having a (meth)acryloyl group, the reaction becomes yh. An unsaturated isocyanate shown in the following formula is produced.

However, the unsaturated isocyanate synthesized from a diisocyanate and an unsaturated monoalcohol is not a single compound as shown in the above formula, but the following σ) diacrylate may coexist.

Since the presence of this diacrylate causes problems with gluing during polymer synthesis, it is necessary to prevent its formation.

In order to prevent the formation of cyacrylate, the reaction may be carried out using a slightly excess amount of diisocyanate relative to the unsaturated monoalcohol.

Monomers that are copolymerized with an unsaturated isocyanate having a (meth)acryloyl group to form a polymer having an isocyanate group in the side chain are as follows: It is desirable that the glass transition temperature is 30°C or less.

Monomers constituting a polymer with a glass transition temperature higher than 30°C, such as styrene, vinyltoluene, methyl methacrylate, acrylonitrile, etc., may be used in combination with monomers that polymerize to give a polymer with a glass transition temperature below 30°C. Although it may be used to increase the adhesive strength, it is not preferable to mix it alone with an unsaturated isocyanate having a (meth)acryloyl group because it reduces the tackiness of the adhesive composition.

The glass transition temperature when polymerized to become a polymer is 30
Examples of monomers having a temperature of 0.degree. lauryl, vinyl acetate,
Examples include vinyl propionate.

The ratio of the unsaturated isocyanate having a (meth)acryloyl group and the 1000-mer compounds is from 1 to 1% of the unsaturated isocyanate.
30 mol% and 70 to 99 mol% of monomers, preferably 5 to 20 mol% of unsaturated isoneanate and 80 to 95 mol% of monomers.

If the proportion of the unsaturated isocyanate having a (meth)acryloyl group used is less than 1 mole, the effect of adding the unsaturated isocyanate is small and the moisture curing property is insufficient;
If the proportion of unsaturated isocyanate having a (meth)acryloyl group used is more than 30%, the pressure-sensitive adhesive also contains isocyanate groups, so as a practical matter, lr: 1 is necessarily required.
'N.

Polymers with side chains [isocyanate groups generally have (
Unsaturated isocyanate-1 having meth)acryloyl group
It is produced by solution polymerization of the unsaturated isocyanate and copolymerizable monomers.

The adhesive having an isocyanate group used in the present invention is, for example, (1) a saturated or unsaturated alkyd having a carboxyl group or a hydroxyl group capable of reacting with two or more isocyanate groups at the end. (2) Polyethers similarly having two or more hydroxyl groups; (3) Polyhydroxyl oligomers obtained by reacting novolak or resol with monoepoxide, etc., which are converted into isocyanates.

Among the above, alkyds are made into isocyanates, and by changing the type and amount of the polyhydric alcohol and polybasic acid components, the physical properties of alkyds can be changed from liquid prepolymers to resins with high softening points. It is best suited for the purposes of the present invention in that it can vary widely.

Isocyanation of an alkyd can be easily carried out by dissolving the alkyd in a monomer and adding it to the isocyanate.

Examples of the polyhydric alcohol component constituting the alkyd include ethylene glycol, diethylene glycol, phlopylene gelicol, dipropylene glycol, neopentyl glycol, trimethylolpropane, glycerin, ethyl acetate, and bisphenol A propylene oxide adduct.

Examples include bisphenol A ethylene oxide adduct.

Examples of polybasic acid components include fucuric anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, pimelic acid, azelaic acid, cepacic acid, maleic anhydride,
Fumaric acid, itaconic acid, tetrahydrophthalic anhydride, hexahydrofucric anhydride, endomethylenetetrahydrophthalic anhydride.

Examples include trimellitic anhydride.

When using a trihydric or higher polyhydric alcohol, a monobasic acid may be used together, and when a polybasic acid is used, a monoalcohol can also be used together.

The proportion of the tackifier having an isocyanate group used is 10 to 200 parts by weight, preferably 30 to 120 parts by weight, per 100 parts by weight of the polymer having an isocyanate group in its side chain. If the proportion of the tackifier having an isocyanate group is less than 10 parts by weight, it is difficult to obtain the effects of the present invention, whereas if the proportion of the tackifier used is more than 200 parts by weight, the tackiness is good, but the initial The moisture-curable pressure-sensitive adhesive composition of the present invention is prepared by mixing a polymer having an isocyanate group in its side chain and a tackifier having an isocyanate group. However, it is preferred that both components be mixed immediately before use. Adding an additive having an anti-moisture absorption effect, such as molecular sheep, to the mixture of both components is extremely useful in improving the stability of the moisture-curable pressure-sensitive adhesive composition.

Moreover, it goes without saying that various additives such as colorants and fillers can be added to the moisture-curable pressure-sensitive adhesive composition of the present invention, if necessary.

〔Effect of the invention〕

The moisture-curable pressure-sensitive adhesive composition of the present invention has excellent tackiness, preservability, and adhesive strength, and is particularly suitable for use as a pressure-sensitive adhesive for moisture-curable pressure-sensitive adhesive tapes.

〔Example〕

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

Example 1 [Synthesis of polymer (A) having an isocyanate group in the side chain] 115 g of butyl acrylate and 7115 g of methyl ethyl ketone were placed in a 1-hole separable flask equipped with a stirrer, a reflux condenser with a moisture-proof device, and a dropping funnel. After charging 06 g of azobisisobutyronitrile, the temperature was 60°C.
222 g (1 mol) of inphorone diisocyanate and 2
-Hydroxyethyl acrylate-1-116,9 (1 mol) 68 g of an unsaturated isocyanate having an acryloyl group (50% methyl ethyl ketone solution) was added dropwise over about 1 hour.Cooled as necessary during the addition. The temperature was maintained at 60°C.

Next, while keeping the temperature at 60°C, the reaction was continued until the polymerization rate reached 95% or higher, and then 0.0% of hydroquinone was added.
5g was added to stop the reaction. Infrared analysis confirmed the presence of free isocyanate groups in the product.

A methyl ethyl ketone solution (polymer content: about 50% by weight) of a polymer (Shu) having an Inciana-1 group in its side chain was obtained in the form of a pale yellow, slightly viscous liquid (viscosity: about 40 poise).

[Synthesis of polyester (B) having isocyanate groups]

Into 11 Mitsuro flasks equipped with a stirrer, a fractionating condenser, and a gas inlet tube with a thermometer, add 17% of Progylene Glycol.
09. Charge 292 g of adipic acid, esterify at 180-190°C until most of the reaction water comes out, then esterify at 210-220°C for 16 hours, and finally remove the fractional condenser and esterify at 10-15 trrrt+ I.
(g) for 1 hour to synthesize a hydroxyl polyester having an acid value of 14° and a hydroxyl value of 64.4. The obtained hydroxyl polyester had a Hazen color number of 500 and was viscous and syrup-like.

After dissolving this hydroxyl polyester 100 parts by weight in 100 parts by weight of methyl ethyl ketone, 26 g of 2゜4-tolylene diisocyanate was added and the mixture was heated and stirred at 60°C for 3 hours. As a result of infrared analysis, disappearance of free hydroxyl groups was observed. It was done.

A methyl ethyl ketone solution of polyester (B) having a solid weight of approximately 55% having isocyanate groups was obtained as a reddish-brown, viscous solution.

100 parts by weight of a methyl ethyl ketone solution of a polymer having an isocyanate group in its side chain (N, 10 parts by weight of a methyl ethyl ketone solution of a polyester (B) having an isocyanate group)
A pressure-sensitive adhesive composition was prepared by mixing 0 parts by weight of molecular sieve and 3 parts by weight of molecular sieve.

As a test piece, length 150 wn, width 25 yn
jrl.

The adhesive composition was applied to the 100+n+++ length end of a steel plate with a thickness of 2 thick, and the adhesive composition was heated at 40 to 45°C in a vacuum dryer equipped with a dehumidifier.
After removing the solvent with 14g of 300ml, a Tetron film with a thickness of 50μ was pressure-bonded.

The physical properties immediately after application and after being left overnight are shown in Table 1, confirming that it is useful as a cured adhesive.

Table 1 A test piece of 25 pieces x 100 scales was pasted on a stainless steel panel. After 20 minutes, 30cb was measured in a 180° direction using a Tensilon tester.The bag was sealed with Silica Dull 209 as a moisture-proofing agent in a bag made from polyethylene-coated aluminum foil.
No abnormality was observed in the adhesiveness of the 5 cm x 20°C adhesive tape with release paper after it was stored at room temperature for one month.

In addition, polyester (B) having an isocyanate group alone is too sticky and cannot be used as an adhesive tape;
The polymer (A) having incyana-1 group in the side chain alone had a very low adhesiveness of 3 or less, making it difficult to use as an adhesive tape.

Example 2 [Synthesis of polymer (C) having an isocyanate group in the side chain] 2-ethylhexyl acrylate was placed in 11 separable flasks equipped with a stirrer, a reflux condenser, a thermometer with a gas introduction tube, and a dropping funnel. 276El.

16 g of acrylonitrile, 1.31 g of isocyanatoethyl methacrylate (manufactured by Dow Chemical Company), 323.9 g of dehydrated methyl ethyl ketone. Pour 35g of azobisisobutyronitrile into a stream of nitrogen gas, ) fi
v-Lf'b/y) 70D? 10 hours at 4B point
When polymerization was carried out, the polymerization rate reached almost 100%.

After 0.06.9% of 1-hydroquinone was added to terminate the polymerization, the product was subjected to infrared analysis, and the presence of free isocyanate groups was confirmed.

It has a viscosity of about 30 poise and is a light yellowish brown color with isocyanate-1 in the side chain.
Methyl ethyl ketone solution of polymer (C) having groups (
A polymer content of approximately 50% by weight was obtained.

[Synthesis of polyetherified phenolic resin (D) having isocyanate groups]

Into 11 separable flasks equipped with a stirrer, a dropping funnel, a reflux condenser with a moisture-proof device, and a thermometer, a resol-type paratertiary-butylphenol resin (about 3 nuclear bodies, melting point about 75°C) and 50 parts by weight of toluene were uniformly charged. After dissolving in the solution, phenolic hydroxy acid and 1 liter of 1 mole of ethylene oxide were added under the catalyst of triethylamine to obtain a toluene solution of polyhydroxylated phenolic resin (hydroxyl value of solid content: 269).

In another identical apparatus, inphoron diisocyanate 1'50
, 9.1-luene 150g, dibutyltin dilaure) 0
．． 5. ! 7. After charging 10 g of Moregular Sheep and mixing uniformly, add 20 g of the toluene solution of the polyhydroxylated phenol resin to this mixture at a temperature of 50 to 60°C.
0 g was added dropwise.

After the dropwise addition was completed, the reaction was carried out at 60° C. for 3 hours, and as a result of infrared analysis, it was determined that the free hydroxyl groups had disappeared.

A toluene solution (resin content of about 50% by weight) of a naturally occurring polyetherified phenolic resin (D) having Inciana-1 group was obtained with a light yellowish brown color and a viscosity of about 260 poise.

100 parts by weight of a methyl ethyl ketone solution of the polymer (C) having an isocyanate group and a toluene solution L of a polyetherified phenol resin (to) having an isocyanate group
A pressure-sensitive adhesive composition was prepared by mixing ooM parts.

A nonwoven fabric made of polyethylene terephthalate having a thickness of 0.2 mm was impregnated with this adhesive composition, and then placed in a vacuum desiccator equipped with dehumidification, and the solvent was removed under reduced pressure of about 200 rnrn Hg.

The resulting double-sided adhesive tape was cut into pieces of 25 mm x 13 mm and adhered to a 150 mm x 25 nm x 31M1 polished steel plate, and then the adhesive strength by tensile shearing was measured.

The same procedure was carried out when the polymer (C) having an isocyanate group and the polyetherified phenol resin (having an isocyanate group) were used alone.

As shown in Table 2, only the pressure-sensitive adhesive composition of the present invention exhibited well-balanced physical properties, and its practicality was recognized.

Table-2 Note) * Notylethyl keto/solution of 7j@l)mer having isocyanate group

Claims (1)

[Claims] (1) (a) 1 to 30 mol% of an unsaturated isocyanate having an acryloyl group or a methacryloyl group and 70 to 99% of monomers copolymerizable with the unsaturated isocyanate.
A moisture-curable pressure-sensitive adhesive composition comprising: a polymer having an isocyanate group in a side chain obtained by reacting with mol %; and (2) a tackifier having an isocyanate group.