JPS581684B2 - Method for producing pressure-sensitive adhesive foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a pressure-sensitive adhesive foam having a predetermined shape such as a tape, sheet, plate, or rod shape, and its object is to produce a pressure-sensitive adhesive foam that is excellent in itself. Adhesive and pressure-sensitive adhesive properties, especially temperature-sensitive properties, and excellent cohesiveness, heat resistance, durability, and workability, as well as good rubber elasticity, making it suitable for waterproofing, soundproofing, and windproofing even in compressed states. The object of the present invention is to provide a foam that can exhibit heat insulating properties and the like.

Conventionally, foam itself has no adhesive strength, so
When pasting this, it is common to use adhesives or pressure-sensitive adhesives, or to use a foam with a pressure-sensitive adhesive coating layer applied in advance, but the former requires complicated installation, while the latter The manufacturing process is complicated and costs are high.

In addition, although the above foam adhesive has good adhesion to rough surfaces, the foam layer and adhesive layer are not integrated, so delamination occurs during long-term use and the adhesive breaks. This causes problems such as adhesive residue on the surface of the adherend and deterioration of waterproofness, soundproofing, heat insulation, etc.

In order to improve these shortcomings, a self-adhesive foam made by adding a foaming agent to rubber and adding a softening agent and a tackifying resin to the foam by crosslinking with heat has been investigated, and the present applicant has reported A patent application is pending for this invention, which exhibits tackiness due to the action of softeners and tackifiers.

This invention is different from the above, and is revolutionary in that the foam itself has excellent adhesive and pressure-sensitive adhesive properties without using a softener or tackifier. and (b) a compound represented by the general formula: (wherein Rl means hydrogen or a methyl group, and R2 means an alkyl group having 2 to 14 carbon atoms) as the main components. and (e) a chain transfer agent and/or a polymerization initiator each having a functional group that reacts with isocyanate. Copolymerizing the agent in a state in which the agent is present in an amount of 0.1 to 20% by weight based on the component (b),
A low molecular weight acrylic copolymer with an average molecular weight of 10,000 or less, which mainly has one functional group at the end of the molecule and one at any position within the molecule, which reacts with incyanate, is obtained, and this low molecular weight acrylic copolymer is This method of producing a pressure-sensitive adhesive foam is characterized in that a raw material mixture is prepared by blending a polyisocyanate and a blowing agent with a polymer, and the mixture is heat-foamed and crosslinked.

The foam obtained by the method of this invention itself has excellent pressure-sensitive adhesive properties and is therefore extremely easy to apply.

Furthermore, since the above-mentioned low molecular weight acrylic copolymer used as a raw material component mainly has one functional group that reacts with incyanate groups at the end of the molecule and one at any position within the molecule, this and the polyin When cross-linked with cyanate, the molecular chain length was relatively long and cross-linked appropriately, unlike general low-molecular-weight acrylic copolymers, in which the above-mentioned functional groups are randomly introduced into the molecule. This gives good results in the heat resistance, durability, and cohesiveness of the resulting foam, as well as pressure-sensitive adhesive properties, especially temperature-sensitive properties (little change in adhesive force over a wide temperature range, especially at high temperatures). In addition, the foam has excellent rubber elasticity, and this rubber elasticity provides excellent waterproof, soundproof, and windproof properties even when used under compressed conditions.
Demonstrates heat insulation properties.

The composition of the raw material mixture prepared in this invention is as follows:
20 to 200 parts by weight of polyisocyanate and 5 parts by weight of a blowing agent per 100 parts by weight of the above acrylic low molecular weight copolymer.
A composition containing up to 50 parts by weight is good, and a composition containing various other additives as necessary is also acceptable.

As the low molecular weight acrylic copolymer, one having an average molecular weight of 10,000 or less obtained by the method described below is used.

This copolymer has two functional groups that react with isocyanate groups, one at the end of the molecule and one at any position within the molecule, but due to the general nature of the polymerization reaction, the number of functional groups other than those listed above may be Of course, there may be some content that has the following.

As the polyinsyanate, difunctional incyanate is preferable.

The blowing agent may be any compound commonly used as a blowing agent that decomposes when heated and generates gases such as nitrogen gas and carbon dioxide, such as azo dicarbonamide and azobisisobutyronitrile. nitroso compounds such as dinitrosopentamethylenetetramine, sulfonyl hydrazide compounds such as para-toluenesulfonylhydrazide, and 4,4'-oxybisbenzenesulfonylhydrazide.

In this invention, in addition to the above-mentioned components, for example, foaming aids such as urea and metal salts of carboxylic acids, fillers such as calcium carbonate, clay, silica, and barium sulfate, plasticizers, tackifiers, colorants, and anti-aging agents. , antifungal agents, antioxidants, ultraviolet absorbers, stabilizers, antiozonants, thixotropic agents, and other commonly used additives may be added, and the type and amount of additives may be determined depending on the purpose. It should be determined appropriately depending on the performance and application.

To produce the foam of this invention, a raw material mixture is prepared as described above, and this is applied to one or both sides of a suitable support sheet using an extruder or the like, and the resulting cured sheet is heated. A method of foaming and crosslinking is adopted, but there is also a method of spreading the above mixture on release paper and foaming and crosslinking in the same way to create a foam without a support, and a method of foaming and crosslinking at the same time as extrusion. Various other methods such as a method using a mold or a method using a mold may be employed.

The thickness of the foam (inner thickness of the foam layer on one side in the case of a foam layer provided on both sides of the support) is usually about 0.1 to 30 mm.

The acrylic low molecular weight copolymer in this invention is (a
) a functional unsaturated monomer having one functional group that reacts with isocyanate; and (b) general formula (wherein R1 means hydrogen or a methyl group, and R2 means an alkyl group having 2 to 14 carbon atoms). It can be easily produced by a method of copolymerizing a monomer mainly composed of the compound represented by (c) in the presence of a chain transfer agent and/or a polymerization initiator each having a functional group that reacts with isocyanate.

In this method, the molar ratio of component (a) to component (b) is set to 1.
:5 to 500, component (c) to 0.1 to 20 of component (b)
% by weight to obtain a low molecular weight acrylic copolymer having one functional group at the end of the molecule and one at any position within the molecule, which reacts with incyanate.

Specific examples of component (a) include acrylic acid, methacrylic acid, maleic anhydride, cinnamate vinyl ester, and 2-hydroxyethyl acrylate (or methacrylate).
, 2-hydroxybutyl acrylate (or methacrylate), glycidyl acrylate (or methacrylate), N-methylaminoethyl acrylate, vinyl bromide, 3-chloro-2-hydroxypropyl acrylate (or methacrylate), and the like.

As component (b), R2 in the above general formula may be branched or unbranched, and specifically, R2 may be an ethyl group, an isobutyl group, a 1-ethylglobyl group, or a 1-methyl group. Examples include pentyl group, 2-methylpentyl group, 3-methylpentyl group, 1-ethylbutyl group, 2-ethylbutyl group, inoctyl group, 3,5,5-trimethylhexyl group, decyl group, dodecyl group, etc. However, when an alkyl group having more than 14 carbon atoms is used as an acrylic copolymer and used as a mixture of the above-mentioned raw materials, there is a problem in adhesiveness as a pressure-sensitive adhesive foam.

The chain transfer agent of component (c) has a carboxyl group as a functional group,
It broadly includes those having a hydroxyl group, an amine group, etc., and which act effectively as a chain transfer agent for copolymerization.

Representative examples thereof include 2-mercaptoacetic acid, 2-mercaptoethanol, and 2-aminoethanethiol.

Further, the above-mentioned polymerization initiator has a functional group such as a carboxyl group or a hydroxyl group, and examples thereof include azopiscyanovaleric acid, peroxidized oxalic acid, and azobiscyanopentanol.

Synthesis of the low molecular weight acrylic copolymer involves combining component monomers (a) and (b) in the presence of a predetermined amount of component (e), that is, a chain transfer agent and/or a polymerization initiator. Copolymerization may be carried out according to a conventional method, and a functional group based on component (c) is introduced at one end of the copolymer molecule by reaction, and a functional group based on component (a) is introduced at any position within the molecule. .

The reaction is radical polymerization, and conventional initiators such as penzoyl peroxide, α・α′-azobisisobutyronitrile, and redox catalysts can be used as the polymerization initiator, but the initiation of the polymerization of component (c) When an initiator is used, it is not necessary to use a conventional initiator.

Even when both initiators are used in combination, the amount of component (c) initiator required for introducing a functional group is usually required in a large amount.

When a chain transfer agent (e) is used in combination, the amount of the polymerization initiator (e) is determined depending on the amount used.

This invention will be explained below with reference to Examples.

The acrylic low molecular weight copolymer used in the examples was manufactured by the following method.

<Acrylic low molecular weight copolymer manufacturing method> A mixture consisting of 60 parts of 2-ethylhexyl acrylate, 40 parts of ethyl acrylate, 5 parts of acrylic acid, 3 parts of 2-hydroxyethyl acrylate, and 2 parts of 2-mercaptoethanol was prepared. 30 wt% of this mixture was placed in a fourth flask and heated to 70°C while stirring and replacing the inside of the flask with nitrogen. After 60 minutes, 0.1 part of α・α'-azobisisobutyronitrile was added. was added dropwise using a dropping funnel over a period of 30 minutes, and the polymerization was terminated when no heat generation was observed.

The obtained copolymer had a polymerization rate of 100%, a viscosity (Brookfield viscosity) of 300 poise, an average molecular weight (by vapor pressure osmosis method) of 7,500, and a number of hydroxyl groups per molecule (calculated from the molecular weight and the number of functional groups measured by alkaline titration). )2.0
Met.

Example 1 Acrylic low molecular weight copolymerization 100 parts by weight 2-functional isocyanate (manufactured by Nippon Polyurethane Co., Ltd. Co 100 Ronate 4
095) Tin octylate 0.5 α・α′-
Azobisisobutylene 20 Ronitrile After thoroughly kneading the mixture having the above composition in a vacuum mixer, it was applied to both sides of a 0.1 mm thick support (Kuraray's cheesecloth vinylon #300) using an extruder and cured to a 2 mm thick layer. Got a sheet.

Next, this cured sheet was preheated at 100° C. for 15 minutes, and then foamed and crosslinked at 140° C. for 30 minutes, resulting in a foam sheet with a thickness of 4 mm.

This sheet had sufficient pressure sensitive adhesive properties.

Example 2 Acrylic low molecular weight copolymerization 100 Parts by weight Calcium carbonate 100 Bifunctional isocyanate 100 (Same as Example 1) Tin octylate 0.5 Petroleum resin
20 parts by weight dinitropentamethylenetetramine 30 A mixture having the above composition was made into a foam sheet having a thickness of 4 mm in the same manner as in Example 1.

This foam exhibited sufficient pressure sensitive adhesion.

<Performance test> Each foam sheet obtained in Examples 1 and 2 was
Sample pieces were cut to a size of 150 mm and tested for adhesion, temperature sensitivity, adhesive residue, density, and fatigue resistance using the following various test methods. Also, heat resistance was tested by kneading through a vacuum mixer in each example. The material was adhered onto the release paper in the same manner as in the example, and the resulting cured sheet was foamed and crosslinked by the same heating operation as in the example to obtain a sheet having a 5 mm thick foam layer, and then the release paper was applied. A sheet consisting only of the foam was obtained by peeling it off, and a test was conducted using a cut piece of 120 mm x 10 mm based on this JIS K6301 Tanbell No. 1 shape.

The commercially available product in the table is a carpet tape having a density of 0.11 g/cm 2 and a thickness of 5 mm, and the surface of the EPT-IIR foam is coated with IIR adhesive.

<Adhesive strength and temperature sensitivity>...JIS Z1528-9
Following the 0° peeling method, after adhering to the adherend under normal conditions, it was stored in a thermostatic oven with hot air circulation for 2 hours, and the adhesive strength at each temperature was measured when it was peeled off at a speed of 300 mm/min. The load was calculated.

<Adhesive residue>...According to the adhesive force measurement method of JIS Z1528, after press-fitting to the adherend under normal conditions, store it in a hot air circulation constant temperature bath at 60℃ and peel it off under normal conditions after a specified period of time has passed. The presence or absence of adhesive residue was measured.

<Density> The volume was determined by measuring the thickness, width, and length, and the density was calculated from the weight.

<Fatigue resistance> A cyclic fatigue test of ±10% was conducted with a joint width of 4 mm using a tensile and compression cyclic fatigue testing machine.

<Heat resistance> A constant temperature bath with hot air circulation was maintained at a constant temperature of 90° C., and the change in 50% modulus at 90° was determined according to the physical test method for vulcanized rubber of JIS K6301.

As is clear from the above test results, the foam of the present invention has excellent adhesive strength, heat resistance, and fatigue resistance, and is highly suitable for adhesion to rough surfaces and as a joint material. Recognize.

In addition, unlike conventional adhesive foams in which the adhesive layer and foam layer are separated, the foam itself has pressure-sensitive adhesive properties, so there is no adhesive residue on the adherend, making it easy to reposition. It peels off at the interface of the adherend, resulting in good workability and excellent adhesive durability.

Moreover, by using a specific acrylic low molecular weight copolymer, the temperature-sensitive properties are good, and the durability test mentioned above shows that it has excellent rubber elasticity. Waterproof, soundproof, windproof,
It can be seen that good results can be obtained in terms of heat insulation.

Claims (1)

[Scope of Claims] 1(a) a functional unsaturated monomer having one functional group that reacts with isocyanate; and (b) a general formula; (wherein R
1 means hydrogen or a methyl group, R2 means an alkyl group having 2 to 14 carbon atoms), and the molar ratio of component (a) to component (b) is 1. :
5 to 500, and (c) a chain transfer agent and/or a polymerization initiator each having a functional group that reacts with incyanate is present in an amount of 0.1 to 20% by weight based on the component (b). to obtain an acrylic low molecular weight copolymer with an average molecular weight of 10,000 or less, which mainly has one functional group that reacts with incyanate at the end of the molecule and one at any position within the molecule, A method for producing a pressure-sensitive adhesive foam, which comprises preparing a raw material mixture by blending this low-molecular-weight acrylic copolymer with a polyisocyanate and a blowing agent, and subjecting the mixture to heat foaming and crosslinking. 2 20 to 200 parts by weight of polyisocyanate and 5 parts by weight of polyisocyanate per 100 parts by weight of acrylic low molecular weight copolymer
The method for producing a pressure-sensitive adhesive foam according to claim 1, wherein a raw material mixture is prepared by blending 50 parts by weight. 3. The method for producing a pressure-sensitive adhesive foam according to claim 1 or 2, wherein the polyisocyanate is mainly composed of a difunctional incyanate.