JPH0193353A - Preparation of foam - Google Patents

Abstract

PURPOSE:To obtain a foam layer having a uniform thickness, no stripe and uniform bubble size, by mechanically stirring a compound containing a rubbery substance emulsion, a crosslinking agent and a foaming agent as essential components to prepare a fine bubble-containing compound and supplying and applying the obtained compound to a support liner from a hermetically closed system to dry the coating layer. CONSTITUTION:As a rubbery substance emulsion, a composition prepared by emulsifying rubbers and synthetic resins according to a usual method is designated. As a crosslinking agent, sulfur, a melamine resin, an epoxy resin, polyisocyanate or the like are used and, as a foaming agent, an anionic, nonionic or amphoteric surfactant is used. The above mentioned compound mixed under stirring is stirred by a stirrer like a high mixer while air is forcibly introduced into the compound to be brought to a fine bubble-containing compound expanded by 1.5-10 times. The prepared bubble- containing compound A is injected in a container of a hermetically closed system and is not gelled because supplied to a support liner 3 from the container of the hermetically closed system immediately before coating. Therefore, application of a stripe to a thin foam layer by a gelled substance or the thickness thereof becoming non- uniform due to the substance is prevented.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing a foam, and more particularly, the present invention relates to a method for producing a foam, and more specifically, a foam that is laminated in a thin layer integrated with a support liner or peeled from a support liner. The present invention provides a method for producing a foam obtained in the form of a thin foam film, and a thin foam film obtained from the method.

<Prior art and its problems> Conventionally, methods for producing foam using a microfoam-containing composition obtained by mechanically stirring a composition containing a rubber-like substance emulsion as a main component include a method of pouring into a mold; Roll coating methods, knife coating methods, etc. are known.

However, the casting method has the problem that not only is it impossible to obtain a long foam sheet, but also that it takes a long time to produce.

On the other hand, in coating methods such as roll coating and knife coating, the fine bubble-containing compound is temporarily accumulated in a portion of the coater and applied to the support liner.

Parts that are in contact with air may partially gel due to external conditions, and this gel may adhere to a portion of the coater or adhere to the inside or surface of the applied compound film. Another problem was that the compound film on the support liner was streaked and had an uneven thickness.

Means for Solving the Problems> The present invention provides a novel method for producing a foam that solves the problems of the prior art, and its gist is as follows:
A mixture containing a rubber-like substance emulsion, a crosslinking agent, and a foaming agent as essential components is mechanically stirred to form a fine foam-containing formulation,
The containing formulation is supplied and coated onto the support liner from a closed system and dried.

According to the process of the invention, the microfoam-containing formulation is.

Since it is a closed system without external restrictions such as air until just before it is supplied onto the support liner, there is no gelling or defoaming of the compound, resulting in streaks or uneven thickness. It is possible to obtain a foam layer or a foam film having uniform cells without any problems.

Rubber-like substance emulsions used in the practice of the present invention include natural rubber and urethane rubber.

Silicone rubber, fluorine rubber, chloroprene rubber.

Rubbers such as nitrile rubber, styrene-butadiene rubber, styrene-imbrene-styrene copolymer rubber, and/or ethylene-vinyl acetate copolymers.

Examples include those obtained by emulsifying synthetic resins such as polymers or copolymers mainly composed of acrylic esters according to conventional methods. The emulsion is.

The solid content is adjusted to 30 to 70% by weight, preferably 50 to 65% by weight.

As the crosslinking agent, sulfur, melamine resin, epoxy resin, polyisocyanate, etc. are used.

As the foaming agent, surfactants such as anionic surfactants such as ammonium stearate, sodium lauryl sulfate, and potassium oleate soap, nonionic surfactants such as polyoxyethylene derivatives, and amphoteric surfactants such as lauryl betaine are used.

These crosslinking agents and foaming agents are added in amounts of 0.3 to 7 parts by weight and 0.1 to 10 parts by weight, respectively, to 100 parts by weight of the solid content of the emulsion to form a blend.

The formulation may optionally contain carboxylated ethyl acrylate, mecellulose, thickeners such as sodium alginate, PH adjusters such as ammonia, caustic soda, polyethylene glycol.

A gelling agent such as polymethyl vinyl ether or sodium fluorosilicide is added to the solid content of the emulsion.
It can be added in a total amount of 0.1 to 20 parts by weight based on 0 parts by weight.

The thus blended mixture is usually adjusted to a viscosity of 10 to 300 voids (at 20 DEG C.) and stirred and mixed uniformly.

The mixture thus stirred and mixed is processed using an oak mixer.
, fine form, high mixer, etc.
Stir while forcing gas into the formulation (stirring speed 5
00-3000r, p, m 20℃), and the bubble diameter is about 30-100. cox, viscosity 30 to 1000 boise (
at 20° C.) to form a formulation containing 1,5 to 10 times as many microbubbles.

The prepared formulation A is poured into a closed container, for example as shown in the figure, and is designed not to come into contact with air until immediately before being supplied to the support liner to prevent gelation. . In the drawings, ] is a closed container, which has a discharge port 2 at the left end. 3 is a support liner, and a predetermined gap is provided so that the outer end of the discharge port 2 of the container 1 does not come into contact with the liner 3. The thickness of 1 mA of the formulation supplied from the discharge port 2 onto the liner is:

Although the width of the discharge port 2 can be freely changed by adjusting the width, it is usually in the range of 30 to 2000 μm.

The supporting liner obtains a laminate with one foam layer or
Alternatively, the choice is made depending on the purpose of obtaining a thin foam film. That is, if a laminate with one foam layer is to be obtained, the support liner itself is selected from a material having an affinity with the formulation comprising the foam layer l-, or the support liner itself is Although the foam has a low affinity, the surface is activated or coated or laminated with an affinity substance to make it compatible with the above-mentioned formulation, and a thin foam layer is firmly attached to the support liner. Glue and integrate. The sheet-like product thus obtained can be used, for example, as a packaging material by taking advantage of its cushioning properties.

On the other hand, if thin foam films are to be obtained, it is necessary that a single layer of foam dried and cured on a supporting liner can be easily peeled from the liner, so that at least the surface of the liner is free from the formulation. It is necessary to have low affinity. These liners include 1 paper, non &
1I cloth, 1 knitted woven cloth.

Plastic films, metal foils, etc. are used.

Also, those whose surfaces have been treated with silicone, fluorine, long-chain alkyl, etc. can also be used.

A layer of a curing formulation applied onto such a liner
i2 Normally pre-dry at 70-95°C for 10-300 seconds to adjust the layer surface to about 80°C to evaporate moisture, then heat at 100-200°C for 100-500 seconds to crosslink and cure, A thin foam layer with a cell diameter of approximately 30-100 μm is obtained.

<Effects> According to the manufacturing method of the present invention, the fine foam-containing formulation is supplied from a closed container onto the support liner immediately before layering, so it does not gel, and therefore the gelled product does not form a foam thin layer. It has the characteristic that a thin foam layer or thin foam film with a uniform thickness can be obtained without streaks or non-uniform thickness.

<Example> Examples of the present invention are shown below. The text middle part means the weight part.

Fruit 7M@1 Acrylic copolymer emulsion 16 with a solid content of 59 fflt% consisting of acrylic acid ether-butyl acrylate-acrylonitrile copolymer (63:28:9 by weight)
9.5 parts, 2 parts of melamine resin, 7 parts of ammonium sulfate
A formulation consisting of 1 part of carboxylated ether acrylate, 2 parts of aqueous ammonia (viscosity 80 voids
20℃) All oak mixer (1500r, p, m
A microfoam-containing formulation (viscosity 150 voids at 20°C) with a foaming ratio of about 2 times and a cell diameter of about 30 to 50 μm is obtained by mechanical stirring at 20°C.

Injecting the conjugate-containing formulation into a closed container of the shape shown in the figure,
The product was discharged from the discharge port onto a support liner (paper) to a thickness of about 200 μm, and then pre-dried and main-dried to obtain a product in which the paper and the foam layer I- were integrated.

The resulting thin foam layer has a uniform thickness, a smooth surface, and a uniform cell diameter of approximately 30-50 μm.

Example 2 Natural rubber emulsion with a solid content of 60% by weight 100 parts sulfur 2 parts potassium oleate soap 3 parts methyl cellulose 1 part aqueous ammonia
2 parts Sodium fluorosilicide
0.5 part A blend consisting of the above composition (viscosity 50
Boise at 20℃) in an oak mixer (500r, p
, mat 20℃) with mechanical stirring to obtain a foaming ratio of 3 times and a bubble diameter of about 50 to 80μ (viscosity 150μ).
Boise at 20°C) is obtained.

Pour the mixture into a closed container of the shape shown.

A laminate in which the polyester film and the foam #fi are integrated by discharging and coating from the discharge port onto a support liner (polyester film whose surface has been treated with adhesive) to a thickness of about 80 μm, and then pre-drying and main drying. I got it.

The resulting thin foam layer has a uniform thickness, a dense and smooth surface, and a uniform cell diameter of approximately 50-80 μm.

Example 3 Nitrile rubber emulsion with dn content of 53% by weight 188.
5 parts sulfur 3 parts sodium lauryl sulfate 2 parts sodium alginate 0.5 parts ammonia water
1 part Sodium fluorosilicide
0.3 parts A mixture (viscosity: 200 voise at 20°C) having the above composition was mixed in an oak mixer (30°C).
00r, p0mat 20°C) with mechanical stirring to create a microfoam-containing formulation with a foaming ratio of 3 times and a bubble diameter of approximately 80 to 100 μm (
Viscosity 500voices at 20°C)? obtain.

Pour the mixture into a closed container of the shape shown.

Peel off the support liner (a release paper made by laminating polyolefin on the surface of kraft paper and forming a silicone thread release layer on top of it) from the discharge port J! Il! Approximately 11cm thick on 1m surface
00μm discharge coating elm, then preliminary and non-drying,
Peel the foam thin layer from the liner surface to a thickness of approximately 1100μ
A conventional thin foam film was obtained.

This thin foam film has smooth and dense surfaces on both the front and back surfaces, and has a uniform cell diameter 'jk of approximately 80 to 100 μm.

Comparative Example The microfoam-containing formulation of Example 1 was coated on a support liner (paper) by roll coating and knife coating and dried to form a single paper and foam thin layer. I got one thing.

The foam thin layer of the resulting laminate has a cell diameter of about 30-20
It was non-uniform with 0μ inertia, and there were countless streaks visible to the naked eye on one surface.

[Brief explanation of the drawing]

The drawing is a schematic explanatory diagram of an apparatus used in the manufacturing method of the present invention. ■...Closed container 2...Discharge port 3...Support liner

Claims (1)

[Claims] 1) A blend containing a rubber-like substance emulsion, a crosslinking agent, and a foaming agent as essential components is made into a microfoam-containing blend by mechanical stirring, and the blend is transferred from a closed system onto a support liner. A method for producing a foam, which is characterized by supplying, applying and drying the foam. 2) The method for producing a foam according to claim 1, wherein at least the surface of the support liner has low affinity.