JPS6134735B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a foam from a synthetic resin emulsion containing a pyrolyzable chemical blowing agent. Mechanical foaming methods and chemical foaming methods are conventionally known as methods for producing synthetic resin emulsion foams. The former mechanical foaming method is a method of manufacturing a foam by mechanically mixing air or other gas into an emulsion, foaming the emulsion, and heating and gelling it. This method requires expensive equipment for foaming, and gelation and melting are required after foaming, and because the foam has good insulation properties, a large amount of heat is required for gelation and melting. In addition, the cells of the resulting foam are easily broken and coarse cells are formed, and the strength thereof is insufficient. On the other hand, the latter chemical foaming method is a method in which a pyrolyzable chemical foaming agent is dispersed in a synthetic resin emulsion, and after molding, the foaming agent is decomposed and foamed after moisture has been removed in advance or while the moisture is being removed. Although this method is easier to operate and superior in productivity than the mechanical foaming method, there are drawbacks depending on the type of synthetic resin used. For example, when acrylic resin is used, large hollow cells tend to occur, and the foam itself often becomes sticky.On the other hand, if small cells are used, the foam becomes hard and brittle, and the expansion ratio is low. descend. In addition, polyurethane emulsions have almost the same problems as acrylic resins, and also have the disadvantage of yellowing. In addition, in the case of vinyl chloride resin emulsion, the cells have large cavities, and the expansion ratio is low.In particular, the middle layer of the foam tends to burst easily, and the cells tend to have larger and larger cavities. In some cases, the expansion ratio is low and it is difficult to obtain a sufficiently expanded foam. In short, the chemical foaming method cannot produce a foam that has a high expansion ratio as a whole, is composed of fine cells, and is soft and has repulsive force. On the other hand, there has been a strong demand for flame retardancy in this type of synthetic resin foam, and attention has been paid to making it flame retardant. Generally, flame retardants are added to make foams flame-retardant, but the use of flame retardants tends to have a negative effect on the foamability and various performances of the foam, and the major drawback is that they generate a lot of smoke. There is. The present inventor has been conducting intensive research in order to resolve the difficulties of chemical reporting methods for synthetic resin emulsions.In particular, (A) ethylene-vinyl acetate copolymer ( below
(B) vinyl chloride resin (PVC) and acrylic resin; The inventors discovered that the desired purpose could be achieved when at least one of the acrylic resins was used in a specific proportion of 75 to 15% by weight, and the invention was completed. That is, the present invention involves dispersing a thermally decomposable chemical blowing agent, a decomposition accelerator, and a filler in a thermoplastic synthetic resin emulsion, and foaming the emulsion to produce a foam. A vinyl copolymer, (B) consisting of at least one of a vinyl chloride resin and an acrylic resin, and 25 to 85% by weight of an ethylene-vinyl acetate copolymer, and at least one of a vinyl chloride resin and an acrylic resin. is 75-15% by weight
The present invention relates to a method for producing a flexible foam characterized by the following. According to the method of the present invention, by using an emulsion of the above-mentioned two or three types of mixed resins in a specific ratio as a synthetic resin emulsion, a soft and flexible foam can be obtained with a sufficiently high expansion ratio and fine-grained cells. A foam consisting of can be obtained. Furthermore, since EVA is used as a component of the synthetic resin, it generates very little smoke, and when combined with fillers, it has excellent flame retardancy even without the use of flame retardants. The EVA used in the present invention can be used as it is with commonly used copolymerization ratios, usually 60 to 95% by weight of vinyl acetate and 40 to 40% by weight of ethylene.
A copolymer with 5% by weight is used. Particularly in the present invention, it is preferable to use a copolymer emulsion obtained by emulsion polymerization of vinyl acetate and ethylene as the EVA. In addition, as the vinyl chloride resin used in the present invention, those used in vinyl chloride resin emulsions for producing this type of foam can be used in a wide range of ways, such as internally or externally plasticized vinyl chloride resin and pastes. An example is vinyl chloride resin powder.
These vinyl chloride resins may be used as latexes or aqueous suspensions, or as powders.
It may be added to EVA emulsion or acrylic resin emulsion. As the acrylic resin used in the present invention, acrylic resins for producing foams of this type, especially emulsions thereof, can be effectively used, and specifically, other polymerizable monomers containing acrylic acid ester as the main component can be used effectively. An example is a copolymer emulsion with. Examples of the polymerizable monomer in this case include styrene, vinyl acetate, acrylonitrile, etc., and also include monomers having carboxyl groups, epoxy groups, amide groups, etc. to impart reactivity. For these acrylic resins, the lowest film forming temperature (hereinafter referred to as
It is preferable that the temperature (referred to as MFT) is 20°C or less. In the present invention, the blending ratio of at least one of PVC and acrylic resin and EVA is particularly limited to the former.
15 to 75% by weight, and the latter 85 to 25% by weight. In this case, if at least one of PVC and acrylic resin does not reach 15% by weight, the foaming ratio will be low and grain retention will be poor. and vice versa, 75% by weight
When the amount exceeds , the expansion ratio tends to be low and the flame retardancy also tends to be low. Also, compared to using either PVC or acrylic resin, this 2
It is preferable to use seeds together. In the present invention, when preparing an emulsion of two or three mixed resins, each resin may be used as an emulsion and each emulsion may be mixed, or a mixture of each resin may be used as an emulsion. Furthermore, an emulsion may be prepared by dispersing the remaining resin in an emulsion of one or two resins. The resin content of the synthetic resin emulsion of the present invention is approximately 30 to 65% by weight. The thermally decomposable chemical foaming agent used in the present invention usually has a decomposition point of about 120 to 220°C, taking into account the melting temperature of the resin in the synthetic resin emulsion, the heat resistance of the base material, and the coating or printing characteristics. It is preferable that the average particle size is about 2 to 8 μm. Examples of such blowing agents include azodicarbonamide and sodium bicarbonate, with azodicarbonamide being particularly preferred. These blowing agents are usually used in an amount of 1 to 20 parts by weight, preferably 3 to 10 parts by weight, per 100 parts by weight of the resin in the emulsion, and are added directly or as an aqueous dispersion to the emulsion. The decomposition accelerator used in the present invention includes substances that promote the decomposition of thermally decomposable chemical blowing agents, such as zinc white, zinc carbonate, zinc stearate, lead carbonate, lead stearate, cadmium stearate,
Examples include urea and salicylic acid, and the amount of these is usually 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight, per 100 parts by weight of the resin in the emulsion. Various types of fillers can be used as fillers in the present invention, but considering dispersibility, coating properties, foaming properties, printability of foam, etc., calcium carbonate, magnesium carbonate, aluminum hydroxide, Preferable examples include magnesium hydroxide, barium hydroxide, ferrous hydroxide, basic zinc carbonate, basic lead carbonate, silica sand, and clay, with an average particle size of 0.1 to 30μ, preferably 0.2
A fine powder of ~10μ is preferred. Among these, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, basic zinc carbonate, basic lead carbonate, and ferrous hydroxide are preferred in view of the flame retardancy of the foam. The amount of these fillers used is 100% of the resin in the emulsion.
Usually 50 to 200 parts by weight, preferably 80 parts by weight
~160 parts by weight. If necessary, a stabilizer for thermally stabilizing the vinyl chloride resin may be added to the synthetic resin emulsion of the present invention. As the stabilizer used in this case, ordinary stabilizers for PVC are widely used, and specific examples include metal soaps such as zinc, tin, and barium. The proportion of these stabilizers used is 0.5 to 3 parts by weight per 100 parts by weight of the resin in the emulsion.
It is about parts by weight. Furthermore, in the present invention, a plasticizer can also be used if necessary. In this case, general plasticizers are widely used as plasticizers,
Examples include dibutyl phthalate, dioctyl phthalate, and 2-ethylhexyl adipate. Furthermore, suitable pigments and dyes can be used in the present invention, such as titanium white,
Aniline black, permanent carmine FB,
Preferred examples include phthalocyanine blue and phthalocyanine green, with water-based pigments, ie, pigment resin colors, being particularly preferred. In addition, in the present invention, dispersants, wetting agents, antifoaming agents, thickeners, film forming aids, antistatic agents,
One or more types of lubricants, antioxidants, etc. may be added as necessary. When preparing the synthetic resin emulsion used in the present invention, first, a blowing agent, a decomposition accelerator, a filler, and if necessary, various other additives such as a thickener, an antifoaming agent, a dispersant, a pigment, etc. are mixed with water. Then, a fine powder paste is prepared by dispersing it using a suitable means such as a sand mill or a ball mill. Next, this is mixed with a synthetic resin emulsion to produce a foamable synthetic resin emulsion. The synthetic resin emulsion thus obtained is placed on a suitable substrate such as paper,
It is applied onto a cloth, board, film, or fiber and heated for about 30 seconds to 5 minutes at a temperature lower than the decomposition temperature of the blowing agent, usually about 60 to 150°C. This heating removes water in the emulsion and turns the resin composition into a semi-gelled or gelled state. In the second half, the gelled product is heated usually at about 150 to 250°C, preferably about 180 to 210°C, for about 20 seconds to 3 minutes to decompose the foaming agent and form a foam. At this time, if the foaming temperature is lower than 150°C, not only will the foaming process take a long time, but the foaming ratio will be low and the surface of the foam will likely become uneven;
If the temperature is higher than this, foaming will be completed in a very short time, making it difficult to adjust the foaming state, and not only will it take a long time to cool down, but some shrinkage will occur during cooling, which is undesirable. After foaming, the product is cooled by appropriate means such as natural cooling, forced air, cooling drum, etc. to produce the desired foam. The foam of the present invention can be embossed. For this embossing, ordinary embossing means can be effectively applied; for example, after foaming, compression molding may be performed using a textured roll. The foam prepared from the synthetic resin emulsion of the present invention has extremely excellent squeezing properties, that is, has a sufficiently high expansion ratio and is soft and flexible, so that embossing with a sufficiently three-dimensional effect can be expected. The foam obtained by the method of the present invention has the following excellent properties. That is, (a) it is possible to obtain a bulletin board with a fine cell structure and a high expansion ratio. (b) In the present invention, as a type of synthetic resin
Since EVA is used, it produces less smoke, and when used in combination with a filler, a foam with excellent flame retardancy can be obtained. Therefore, since there is no need to use flame retardants, there are no disadvantages caused by flame retardants. (c) Embossing is easily performed and grain retention is good. (d) Excellent printability and water resistance. (e) Unlike conventional polyvinyl chloride resin foams, there is very little risk of pollution such as hydrogen chloride, plasticity, exhaust and volatilization of solvents, etc., and the foams of the present invention do not necessarily require plasticity; Contamination of the foam due to migration, leaching, etc. is also extremely low. (F) The foam of the present invention can be produced by changing the blending ratio of EVA, PVC, and acrylic resin.
It is possible to obtain a product that has the feel and feel of soft tanned leather such as goat leather, and it is also possible to obtain a material that has the feel and feel of suede without any special raising treatment. Therefore, the foam of the present invention can be expected to have a wide range of uses, such as hats,
Accessories and ornaments such as gloves, bags, handbags, belts, and accessory cases; clothing such as coats, suits, jackets, and skirts; chair upholstery, furniture coverings, wall materials, flooring materials, ceiling materials, and carpet lining materials. It can be effectively applied to fields such as (g) The foam of the present invention has excellent water vapor permeability, and therefore, when the foam of the present invention is applied to wall covering materials, the adhesive applied to the back surface dries extremely quickly during pasting. Furthermore, it has adequate moisture permeability to the extent that no condensation occurs on the surface of the wall covering material. Example 1 A foamable synthetic resin emulsion was prepared by blending various substances shown in Table 1 at a predetermined mixing ratio, and a foam was prepared according to the following method. That is, powders such as a decomposition accelerator, a foaming agent, a filler, and TiO ₂ are dispersed in water together with a dispersant, a wetting agent, and an antifoaming agent. Meanwhile EVA
An emulsion, an acrylic ester emulsion, and a vinyl chloride resin latex are mixed to form a mixed emulsion, which is mixed with the above powder dispersion, and then a stabilizer is added as an emulsion to form a foamable emulsion. This emulsion was applied to the paper surface so that the thickness of the sheet after drying was 0.15 to 0.20 mm, and after drying at 120℃ for 3 minutes,
It was heated in an open oven heated to 200°C for 1 minute to foam. The appearance, feel, expansion ratio, squeezing property, flame retardance, and moisture permeability of the obtained foam were measured. The results are shown in Table 2. However, various physical properties were measured using the following methods. Foaming ratio: Thickness after foaming / Thickness before foaming (times) Squeezability: Immediately after foaming, pass through a squeezing roll and measure grain retention after leaving at room temperature for 3 months Flame retardancy: Ministry of Construction notification Evaluation based on fire protection material test standards according to No. 1231 and No. 1828 Moisture permeability: 40% by weight cup method according to JIS ZO208
It was conducted under the conditions of ℃ and 90%RH, and the moisture permeability data are shown.

【table】

[Front] Example 2 Flame-retardant wallpaper lining paper [Kishu Paper Co., Ltd. "E-80MK"]
300% of the foaming emulsion No. 2 of Example 1 was added to
It was coated using a reverse coater at a rate of g/m ² and then dried for 45 seconds using a hot air dryer at 140°C. The coating thickness after drying was 0.13 mm. Next, a pattern for wall covering was printed using a gravure printing machine, heated in an oven at 230°C for 1 minute, and then a grain was immediately formed using a cooled squeeze roll with a woven texture to obtain bulky wallpaper. Ministry of Construction Notification No. 1 regarding newly acquired wallpaper
The results of the fire protection material tests according to No. 1231 and No. 1828 are shown in Table 3.

[Table] The moisture permeability of the wallpaper was also measured according to JIS Z0208, and the results were as shown in Table 4 below. Compared to conventional foamed PVC wallpaper as a comparative example, it had excellent water vapor permeability.

[Table] Example 3 No. 3 foamable synthetic resin emulsion of Example 1
Three types of emulsions were prepared by separately adding 5 parts by weight of phthalocyanine blue, permanent carmine FB, and benzidine yellow coloring pigments to 100 parts. Next, each of these emulsions was screen printed on cotton cloth,
After drying at 110℃ for 2 minutes, put it in a heating oven at 200℃.
The foam was heated for 20 seconds.

Claims (1)

[Scope of Claims] 1. A pyrolytic chemical blowing agent, a decomposition accelerator, and a filler are dispersed in a thermoplastic synthetic resin emulsion,
Regarding producing a foam by foaming this, the thermoplastic synthetic resin consists of at least one of (A) ethylene-vinyl acetate copolymer, (B) vinyl chloride resin and acrylic resin, and ethylene-acetic acid A method for producing a flexible foam, comprising 25 to 85% by weight of a vinyl copolymer and 75 to 15% by weight of at least one of a vinyl chloride resin and an acrylic resin. 2 The pyrolytic chemical blowing agent is asodicarbonamide, and its blending ratio is equal to the resin content in the emulsion.
The manufacturing method according to claim 1, wherein the amount is 3 to 10 parts by weight per 100 parts by weight. 3. The manufacturing method according to claim 1, wherein the vinyl chloride resin is an internally or externally plasticized vinyl chloride resin latex, or an aqueous suspension obtained by externally plasticizing a paste vinyl chloride resin. 4. The production method according to claim 1, wherein the acrylic resin is a copolymer of an acrylic ester and another polymerizable monomer, and the minimum film forming temperature of the polymer film is 20°C or less. 5 The filler is at least one of magnesium carbonate, magnesium hydroxide, aluminum hydroxide, basic zinc carbonate, basic lead carbonate, and ferrous hydroxide, and has a particle size of 0.2 to 10μ; The manufacturing method according to claim 1, wherein the blending ratio is 80 to 160 parts by weight per 100 parts by weight of the resin in the emulsion.