JPH09291167A - Foamable resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamable resin compsn. of which the timing of resin melting coincides with that of blowing agent decomposition and which exhibits an improved foaming behavior by compounding a specific acrylic resin dispersion with a thermally decomposable blowing agent, a decomposition accelerator, and a filler. SOLUTION: 100 pts.wt. (in terms of the solid resin) acrylic resin dispersion contg. a (meth)acrylic ester homo- or copolymer and having a Ti value of -5 to 20 deg.C and lowest film forming temp. of not more than 15 deg.C is compound with 0.5-10 pts.wt. thermally decomposable blowing agent, 0.2-8 pts.wt. decomposition accelerator, and 50-200 pts.wt. filler having a particle size of 0.1-30μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a foam resin composition.

[0002]

2. Description of the Related Art As a method for obtaining a foam of an acrylic resin emulsion, for example, a foam stabilizer is added to an acrylic resin emulsion, and a gas such as air or nitrogen gas is mixed while stirring at high speed, and the resulting mixture is used as a base. A method is known in which a material is coated or cast and then heated to remove water, thereby forming a foam. However, this method has a drawback in that a special device is required or a resin composition is limited in order to mix gas. In addition, it is uneconomical because a large amount of expensive foam stabilizer such as silicone foam stabilizer must be added so that the mixed gas is retained in the resin until after the drying. Further, a synthetic resin is mixed with a thermally expansive resin in which low boiling point hydrocarbons such as pentane, hexane and butane are impregnated or encapsulated and an acrylic resin emulsion, and this mixture is heated after coating or casting on a base material to remove moisture. There is also known a method in which the removal and the expansion of the heat-expandable resin are simultaneously performed to form a foam. In this method,
Since low boiling point hydrocarbons are flammable, there is a risk of explosion and the like, which is not preferable. In addition, in order to obtain a foam having a high expansion ratio, a large amount of heat-expandable resin must be used, but the large use of the resin causes a decrease in mechanical strength of the foam. Further, since the resin is expensive, it is uneconomical to use it in a large amount.

Furthermore, a heat-expandable resin preheated and expanded,
There is also known a method in which a hollow material such as resin hollow beads or hollow glass is mixed with an acrylic resin emulsion, and this is coated on a substrate or cast and then heated to remove water to obtain a foam. However, since the hollow material used here has a large difference in specific gravity from the acrylic resin emulsion, it is difficult to mix it uniformly. Further, in order to obtain a foam having a high expansion ratio, it is necessary to add a large amount of hollow material, which causes a problem that the mechanical strength of the obtained foam is lowered. Hollow materials are also expensive. On the other hand, attempts have also been made to blend a pyrolytic foaming agent into an acrylic resin emulsion to obtain a foam, but the timing of melting the resin and decomposing the foaming agent to release gas does not match. No satisfactory foam has been obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acrylic resin foam which is in a good foaming state in which the timings of resin melting and foaming agent decomposition coincide with each other in order to solve the above problems. is there.

[0005]

The present invention is -5 ° C to 20 ° C.
The present invention relates to a foam resin composition having a Ti value of ° C and a minimum film forming temperature of 15 ° C or lower, containing an acrylic resin emulsion, a thermal decomposition type foaming agent, a decomposition accelerator and a filler. According to the foam composition of the present invention, it is possible to obtain an acrylic resin foam in which fine bubbles are uniformly dispersed and the surface condition is good.
Since the foam composition of the present invention is a water-dispersed system, there is little environmental pollution at the time of its production, and it is also excellent in safety for the human body. Also, the foam obtained is a foam of a material mainly containing vinyl chloride. Since it does not emit a large amount of toxic gas by burning like the body, it can be used in a wide industrial range such as building interior materials.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The foam composition of the present invention contains an acrylic resin emulsion, a thermal decomposition type foaming agent, a decomposition accelerator and a filler as active ingredients. The acrylic resin emulsion used as the resin component usually has a Ti value of -5 to 20 ° C, preferably -3 to 18 ° C, and the minimum film forming temperature is usually 15
C. or less, preferably 14.degree. C. or less. The Ti value is the temperature at which a film obtained by air-drying an acrylic resin emulsion has a towable modulus of 300 kg / cm ² . The minimum film forming temperature is the minimum temperature required to form a continuous film from an acrylic resin emulsion. When the Ti value is less than -5 ° C, the viscosity of the resin is remarkably lowered by the heating for decomposing the foaming agent, and it becomes difficult to retain the gas generated by the decomposition of the foaming agent in the resin, which causes outgassing. However, the expansion ratio does not increase, the gas concentrates on a part of the cells, the bubbles become coarse, or the surface of the foam becomes rough, so that a foam in a good foaming state cannot be obtained. When the Ti value exceeds 20 ° C., the resin does not melt to a viscosity suitable for gas generation at the temperature at which the foaming agent decomposes to generate gas, and only a foam having a low expansion ratio can be obtained. . Even when the minimum film-forming temperature exceeds 15 ° C, the foaming agent decomposes and gas is generated at a temperature at which the resin does not melt to a viscosity suitable for gas generation and retention, and only a foam having a low expansion ratio is produced. I can't get it.

The acrylic resin emulsion of the present invention is not particularly limited as long as it has a Ti value and a minimum film-forming temperature within the above ranges, and those produced by a known method such as emulsion polymerization or solution polymerization are used. Either can be used. Specific examples of the acrylic resin emulsion include homopolymers and copolymers of methacrylic acid esters, homopolymers and copolymers of acrylic acid esters, and the like. As the copolymerization component of the above-mentioned copolymer, any known monomer having a polymerizable double bond such as a vinyl group and a crosslinkable group such as an isocyanate group can be used, and examples thereof include acrylonitrile, styrene and vinyl acetate. , Vinyl chloride, urethane and the like, and one or more of these can be used. Even if the acrylic resin emulsion has a Ti value and / or a minimum film-forming temperature which are not within the above-specified range, the mixture of two or more kinds of the acrylic resin emulsion may be mixed with the resin of the present invention. It can be used as a component.

Further, in the foam composition of the present invention, T
If the i value and the minimum film-forming temperature are within the above ranges, a resin emulsion other than the acrylic resin emulsion can be used together within a range that does not impair the effects of the composition of the present invention. Examples of the resin emulsion include vinyl acetate resin emulsion, vinyl chloride resin emulsion, urethane resin emulsion, ethylene-vinyl acetate copolymer resin emulsion, vinyl acetate-veova copolymer resin emulsion, ethylene-vinyl acetate-vinyl chloride copolymer. Examples thereof include polymer resin emulsions, and one or more of these can be used.

The second active ingredient of the foam composition of the present invention, which is a thermal decomposition type foaming agent, is a known compound which is a solid or liquid at room temperature and releases a gas when heated above the decomposition temperature. Any of them can be used, and examples thereof include organic systems such as azodicarbonamide, azobisisobutyronitrile, p, p'-oxybis (benzenesulfonylhydrazide), p-toluenesulfonylhydrazide, N, N'-dinitrosopentamethylenetetramine. Foaming agent, sodium bicarbonate,
An inorganic foaming agent such as ammonium carbonate can be used. Among these thermal decomposition type foaming agents, azodicarbonamide is particularly preferable in consideration of safety, handleability, amount of released gas, economy and the like. The blending amount of the thermal decomposition type foaming agent is not particularly limited, and can be appropriately selected from a wide range depending on the types of the acrylic resin emulsion to be used in combination, other components, the intended use of the foam to be obtained, etc. 0.5 to 10 parts by weight, preferably 1 to 8 parts by weight with respect to 100 parts by weight of the resin content (the total amount of the resin content of the resin emulsion and the acrylic resin emulsion when other resin emulsions are included). It is about part by weight.

The foam composition of the present invention contains a decomposition accelerator as a third component in order to adjust the decomposition temperature of the thermal decomposition type foaming agent. As the decomposition accelerator, known compounds can be used, for example, metal oxides such as zinc oxide and lead oxide, metal carbonates such as zinc carbonate, potassium carbonate and lead carbonate,
Metal chlorides such as zinc chloride and potassium chloride, metal soaps such as zinc oleate, zinc stearate and cadmium stearate, zinc 2-ethylhexoate, zinc benzenesulfinate, zinc p-toluenesulfinate, urea and the like. You can Among these, zinc acetate, zinc carbonate, zinc 2-ethylhexoate, zinc benzenesulfinate, urea and the like can be preferably used. The decomposition accelerators can be used alone or in combination of two or more. The amount of the decomposition accelerator is not particularly limited, and can be appropriately selected from a wide range depending on the type and amount of the acrylic resin emulsion used in combination, the thermal decomposition type foaming agent and the like, the intended use of the foam to be obtained, and the like. Usually, about 0.2 to 8 parts by weight, preferably 0.3 to about 10 parts by weight of the resin content in the resin emulsion.
It may be about 5 parts by weight.

A filler is added as a fourth component to the foam composition of the present invention. The filler is not particularly limited and any known filler can be used, but considering dispersibility in a resin emulsion, coatability on a substrate or printability, foamability, etc., for example, calcium carbonate, magnesium carbonate,
Aluminum hydroxide, magnesium hydroxide, barium hydroxide, clay, talc, silica sand and the like can be preferably used, and one kind or two or more kinds thereof can be used. The particle size of the filler is not particularly limited and can be appropriately selected from a wide range, but it is usually about 0.1 to 30 μm, preferably about 0.1 to 20 μm. Also, the amount thereof is not particularly limited,
It is usually about 50 to 200 parts by weight, preferably about 55 to 180 parts by weight, relative to 100 parts by weight of the resin component in the resin emulsion. Further, the foam composition of the present invention may contain general additives which are mixed with conventional foam compositions. Examples of the additive include a stabilizer, an antioxidant, an ultraviolet absorber, a colorant, a flame retardant, a reinforcing material, a whitening agent, a thickener, a lubricant, an antibacterial agent, a film forming agent, a dispersant, and a deodorant. A foaming agent, a freeze-thaw stabilizer, etc. can be mentioned, and these 1 type (s) or 2 or more types can be used.

The foam composition of the present invention is prepared by a known method, for example, a foaming agent, a decomposition accelerator, a filler and, if necessary, an additive, a high speed stirrer, a kneader, a sand mill, a ball mill, It can be produced by mixing with a general stirrer such as a paint mill and mixing the resulting mixture with an acrylic resin emulsion. Further, when mixing with a stirrer, a foaming agent can be more uniformly dispersed by adding an appropriate amount of a solvent (for example, water) to make the mixture into a paste. The foam composition of the present invention thus obtained can be made into a foam according to a known method. For example, the foam composition of the present invention may be applied or printed on a substrate having an appropriate material and shape, dried to remove water, and then heated to a temperature above the temperature at which the foaming agent decomposes to foam. .

The base material to which the foam composition of the present invention can be applied is not particularly limited and may be, for example, any of metal, synthetic resin, ceramics, wood, papers, fibers and the like. More specifically, for example, a synthetic resin board, paper, cloth, gypsum board, pearlite board, fiber base board and the like can be mentioned. A known method can be adopted for coating, and examples thereof include a knife coater and a roll coater, and a method of spraying. Also, a known method can be adopted for printing, and examples thereof include a method using a general printing machine such as a silk screen printing machine and a rotary screen printing machine. The coating or printing amount can be appropriately selected from a wide range depending on the intended use of the obtained foam, etc., but normally the film thickness after drying may be about 0.1 to 0.5 mm.

Drying is carried out according to a conventional method, for example, using a dryer such as an electric heater type hot air oven, an LPG combustion type hot air oven, an oil combustion type hot air oven, etc., at a temperature at which the foaming agent does not decompose (usually 70 to 140 ° C.). About 30 seconds to 5 minutes. Foaming after drying to remove water content is performed for 15 seconds to 4 minutes, preferably 20 seconds, at a temperature equal to or higher than the temperature at which the foaming agent decomposes (usually about 170 to 250 ° C, preferably about 180 to 240 ° C). It is performed by heating for about 3 minutes. Although the heating method is not limited, it is usually carried out in a foaming furnace such as an infrared heating foaming furnace, an electric heater type hot air foaming furnace, an LPG combustion type hot air foaming furnace, an oil combustion type hot air foaming furnace. When foaming the foam resin composition of the present invention,
In order to improve the design of the resulting foam, a paint or the like may be separately printed on the surface of the foam, or embossing or the like may be performed.

[0015]

The present invention will be specifically described below with reference to examples and comparative examples. In the following, "part" and "%"
Unless otherwise specified, "parts by weight" means
And "% by weight".

Examples 1 to 6 and Comparative Examples 1 to 4 Azodicarbonamide (foaming agent, uniform AZ H-25), zinc oxide (decomposition accelerator) at the compounding ratios (parts) shown in Tables 1 and 2 below. Ground calcium carbonate (filler),
Aluminum hydroxide (filler), titanium diacid (pigment),
Nopco Santo R [dispersant, San Nopco Co., Ltd.], Liponox NCI [wetting agent, manufactured by Lion Oil & Fat Co., Ltd.], Nopco 8034 [defoamer, San Nopco Co., Ltd.], Modicol L [stabilizer, San Nopco Co., Ltd.] Co., Ltd.] was dispersed in 20 parts of water, and this was mixed with a resin emulsion having a mixing ratio (parts) shown in Tables 1 and 2 to produce a foamable resin emulsion of the present invention. The foamable resin emulsion was applied to flameproof paper for wallpaper with a knife coater so that the film thickness after drying was 0.15 mm, and dried for 3 minutes with a hot air dryer at 120 ° C. Next, it was heated in a hot air foaming furnace at 200 ° C. for 1 minute to foam. Expansion ratio of the obtained foam,
Table 3 shows the bubble state, the surface state and the comprehensive evaluation. Foaming ratio = film thickness after foaming / film thickness before foaming Bubble state: The cross section of the film after foaming was visually observed. Surface state: The surface of the film after foaming was visually observed. The overall evaluation is as follows. ⊚: excellent ： good △: bad

[0017]

[Table 1]

[0018]

[Table 2]

The resin emulsions A to I used in Tables 1 and 2 are specifically as follows. A ... Acrylic ester copolymer resin emulsion, resin concentration 50% B ... Acrylic-styrene copolymer resin emulsion, resin concentration 48% C ... Ethylene-vinyl acetate-acrylic copolymer resin emulsion, resin concentration 50% D ... Acrylic-vinyl acetate copolymer resin emulsion,
Resin concentration 46% E ... Vinyl acetate-Veoba copolymer resin emulsion, resin concentration 48% F ... Ethylene-vinyl acetate copolymer resin emulsion,
Resin concentration 50% G ... Ethylene-vinyl acetate-vinyl chloride copolymer resin emulsion, resin concentration 49% H ... Acrylic ester copolymer resin emulsion, resin concentration 46% I ... Acrylic-styrene copolymer resin emulsion, resin 48% concentration

[0020]

[Table 3]

From Table 3, the acrylic resin foams obtained from the composition of the present invention, Comparative Example 1 (Ti value is not specified), Comparative Example 2 (Ti value and minimum film forming temperature are not specified), Comparative Example 3
The expansion ratio is higher than that of the acrylic resin foams (containing no filler) and Comparative Example 4 (containing no decomposition accelerator),
It is clear that the bubble state is slightly finer on average, although slightly larger, and the surface state is smoother on average, although slightly rough.

[0022]

INDUSTRIAL APPLICABILITY In the present invention, a thermal decomposition type foaming agent is added to an acrylic resin emulsion having a specific Ti value and a minimum film forming temperature, followed by drying and foaming to melt the resin and decompose the foaming agent. The timing is the same, and an acrylic resin foam having a good foaming state can be obtained.

Claims (2)

[Claims] 1. A foam containing an acrylic resin emulsion having a Ti value of −5 ° C. to 20 ° C. and a minimum film forming temperature of 15 ° C. or lower, a thermal decomposition type foaming agent, a decomposition accelerator and a filler. Resin composition. 2. The foam resin composition according to claim 1, wherein the acrylic resin emulsion is at least one selected from homopolymers of acrylic acid esters and copolymers of acrylic acid esters and other copolymerization components. Stuff.