JPH0455620B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a foam made of unsaturated polyester resin, in which ammonium hydrogen carbonate powder is mixed as a foaming agent into liquid unsaturated polyester resin and foamed. The present invention relates to a method for foaming an unsaturated polyester resin containing an organic peroxide and a curing accelerator, and foaming and curing the resin under heating in the absence of water. [Prior art] Conventionally, unsaturated polyester resins are inexpensive;
Due to its strength and excellent heat resistance, it is used in furniture, bathtubs, ships, structural materials, etc. By taking advantage of these excellent properties and further foaming, it has light weight, heat insulation, good feel, and good workability, and its uses can be dramatically expanded. However, the reason why unsaturated polyester resins are not widely used in industry is that their curing behavior is very different from that of other resins, and therefore it is very difficult to foam them. That is, unsaturated polyester resin compositions are normally liquid and fluid, but as the polymerization reaction progresses, their viscosity rapidly increases and gels. This is because the time for the foam to maintain its viscosity is extremely short, and even if a foaming agent is used, it is extremely difficult to decompose the foaming agent during this period. Despite these difficulties, there is a strong demand for foams or lightweight bodies, and various methods for making foams are known. All of these are based on the principle that when the unsaturated polyester resin is in a liquid state, a foaming agent is included in the unsaturated polyester resin, and the foamed state is polymerized and cured. One of the methods is to use air or other gas as a blowing agent, to include it in a liquid material under normal pressure or pressurization, and to generate bubbles with the gas. However, it is difficult to stabilize the bubbles using this method, and the bubbles that are generated are generally coarse and it is difficult to generate fine bubbles. The second method is to use a compound that generates gas through the reaction of two compounds as a blowing agent, and when the resin reaches an appropriate viscosity during the curing process, the gas from the blowing agent is used. The purpose is to foam the foam. As a blowing agent of this reaction type, for example, there is a method in which isocyanate and water are reacted. Furthermore, a method is also known in which a ternary mixture of carbonate, acid, and water is simultaneously added as a blowing agent to an unsaturated polyester resin, thereby causing foaming. Furthermore, we proposed a method in which sodium bicarbonate and acetic acid are mixed in a substantially anhydrous state, and a small amount of water is added later to cause foaming, thereby controlling the hardening of the resin and the timing of action of the foaming agent. has been done. However, these foaming agents generate gas from the time they are mixed with acid or water, and foaming occurs at low temperatures. Therefore, in order to cure in a foamed state, the curing must be adjusted to match the low temperature.
For this reason, it takes a long time for the resin to harden, and the bubbles become coarse, resulting in poor working efficiency and high costs when used industrially. A third method includes a method in which a compound that decomposes when heated to generate gas or a liquid that easily vaporizes when heated is used as a blowing agent. As the heating type blowing agent, a method using, for example, toluenesulfonyl hydrazide, and a method using carbon dioxide gas generated during decomposition of carbonate ester anhydride have also been proposed. Furthermore, a method is also known in which expandable microcapsules are added and heated to expand into microballoons and simultaneously harden the resin. [Problems to be solved by the invention] However, the conventional third method uses a special blowing agent and has the disadvantage of being expensive industrially. There are many problems and the situation is industrially difficult. In view of the above circumstances, the present inventors have developed a compound that is inexpensively available, economically advantageous, and generates a large amount of gas.
Generally, we focused on ammonium hydrogen carbonate, which is used in the second method to generate gas by reacting it with acid and water. As a result of extensive research into the conditions such as the content of curing agents and curing accelerators that can be used when foaming unsaturated polyester resins, we found that when ammonium hydrogen carbonate powder is mixed with unsaturated polyester resins and foamed, curing Contains organic peroxide and curing accelerator as agents,
By foaming and curing under heating in the absence of water, it is possible to easily obtain a foam having uniform, fine cells that is industrially economical and completely unexpected from conventional methods. This is the discovery of a foaming method. Ammonium bicarbonate, which is available at low cost, is decomposed by acid and water to generate gas, and also generates gas by heating itself. The present invention takes advantage of this property and provides an industrially advantageous foaming method adapted to this property.
In order to foam a resin, it is necessary for the resin to contain gas without letting it escape, and to be soft enough to expand under gas pressure. In other words, the viscosity of the resin must be within a range suitable for foaming. When it is within this range, it is necessary to cure it quickly, and it can be carried out industrially and efficiently. Therefore, in the second method, in which gas is generated at low temperatures, a curing accelerator is used in combination with the curing agent to accelerate curing in order to match the curing at this low temperature. Further, in the third method in which gas is generated by heating, only a curing agent is added because heating has a curing effect. Generally, only a curing agent is used for heat curing, and the use of an accelerator is limited to room temperature curing. However, in order to obtain a fine and good foam, the timing of the decomposition and foaming of the blowing agent and the gelation and curing of the resin is an important point, but research has shown that the timing cannot be achieved with the curing agent alone, or that good foaming occurs. However, it was discovered that by using an accelerator in combination, the timing can be adjusted freely by adjusting the amount. That is, the present invention provides a foaming method in which a curing agent and a curing accelerator that are compatible with the properties of ammonium hydrogen carbonate are used in combination under heating, and the ammonium hydrogen carbonate is foamed and cured in the absence of water. An object of the present invention is to provide a method for foaming an unsaturated polyester resin that, when carried out industrially, can significantly shorten the molding time, can be provided at low cost, and can yield a foam having uniform and fine cells. [Means for Solving the Problem] The structure of the present invention to achieve this object is to mix ammonium bicarbonate powder as a blowing agent with a liquid unsaturated polyester resin, and mix organic peroxide as a hardening agent and hardening accelerator. The gist of this method is to contain a filler if necessary, and to foam and harden it in the absence of water and under heat. The unsaturated polyester resin used in the present invention refers to unsaturated aliphatic dibasic acids such as maleic acid and fumaric acid or their acid anhydrides, ester-forming derivatives such as lower alkyl esters, or their combination with phthalic acid or adivin. An unsaturated polyester obtained by polycondensing an unsaturated polybasic acid such as an acid or an ester-forming derivative such as its acid anhydride or lower alkyl ester with a polyhydric alcohol such as polypropylene glycol or diethylene glycol, Liquid unsaturated polyester resin obtained by dissolving it in a copolymerizable monomer (e.g., styrene, diallyl phthalate, etc.) having an unsaturated bond (e.g., vinyl group, allyl group, etc.) that can be copolymerized with saturated polyester. say. Specific examples of the unsaturated aliphatic dibasic acids and their ester-forming derivatives include maleic acid,
Examples include phthalic acid, citraconic acid, itaconic acid, maleic anhydride, itaconic anhydride, and the like. Further, specific examples of the unsaturated polybasic acid and its ester-forming derivatives include phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, tetrahydrophthalic acid, Tetrabromophthalic acid, hettic acid, succinic acid, adivic acid, azelaic acid, sebacic acid, trimellitic acid, phthalic anhydride, tetrachlorophthalic anhydride,
Examples include tetrabromophthalic anhydride, endomethylenetetrahydroic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic anhydride, and trimellitic anhydride. Furthermore, specific examples of the polyhydric alcohol include:
Ethylene glycol, propylene glycol, butanediol-1,4, butanediol-1,3,
butanediol 2,3, diethylene glycol,
Dipropylene glycol, triethylene glycol, pentanediol 1,5, hexanediol 1,6, neopentyl glycol, 2,2,4-
Trimethylpentanediol 1,3, hydrogenated bisphenol A, 2,2-di(4-hydroxyproboxyphenyl)propane, pentaerythritol diallyl ether, trimethylene glycol,
Examples include 2-ethyl-1,3-hexanediol. Specific examples of the copolymerizable monomer include styrene, vinyltoluene, chlorostyrene, 2-methylstyrene, divinylbenzene, methyl methacrylate, methyl acrylate, ethyl acrylate, vinyl acetate, diallyl phthalate, and triallyl sia. nurate, diallylbenzene phosphonate, N-
Examples include vinylpyrrolidone, maleimide, acrylonitrile, and the like. The amount of the copolymer used is preferably 10 to 70% by weight based on the total amount of the unsaturated polyester and the copolymerizable monomer. If the amount used is as small as less than 10% by weight, the viscosity of the unsaturated polyester resin becomes high, making foam molding difficult and the mechanical properties of the resulting foam deteriorated, which is not preferable. on the other hand,
If the amount exceeds 70% by weight, it is not preferable because the chemical resistance and heat resistance of the obtained foam will deteriorate. The ammonium bicarbonate powder used as a blowing agent in the present invention has a molecular formula of NH ₄ HCO ₃ = 79.06, and is also known as ammonium bicarbonate. When exposed to carbon dioxide under pressure, crystals precipitate. It was obtained by dissolving this in water, recrystallizing it with ethanol, and purifying it. In the present invention, a finely divided powder is used, preferably having a particle size of 30 microns or less. This is because if the diameter exceeds 30μ, it is difficult to obtain uniform, fine cells, and a preferable foam cannot be obtained. The amount of ammonium hydrogen carbonate powder to be used can be arbitrarily selected depending on the desired expansion ratio of the foam, but it is
0.1 to 20 parts by weight are used, preferably 0.2 to 10 parts by weight. If the amount is less than 0.1 parts by weight, the foamability is unfavorable, and if it exceeds 20 parts by weight,
Too much gas is generated, making it difficult to balance the viscosity of the resin, which may cause cracks in the foam, and is also unfavorable from an economic point of view. In the present invention, the unsaturated polyester resin and ammonium hydrogen carbonate powder are foamed and cured under heat in the absence of water. When polymerizing and curing this mixture, the curing agent used is an organic peroxide. These include, for example, ketone peroxide systems (e.g. methyl ethyl ketone), hydroperoxide systems (e.g. cumene hydroperoxide), diacyl peroxide systems (e.g. benzoyl peroxide), peroxycarbonate systems (e.g. diisopropyl peroxide), etc. carbonate),
Organic peroxides such as peroxyesters (eg, hebutyl peroxyacetate) and combinations thereof can be used. The curing accelerator used in combination with the above curing agent includes, for example, naphthenic cobalt, octoethane cobalt, naphthenic magan, naphthenic copper, naphthenic zinc, lauryl mercaptan, dimethylaniline, triethanolamine, diethylenetriamine, pyridine, viveridine, etc. and they can be used in combination. The purpose of using the curing agent and curing accelerator in combination is to thermally decompose the ammonium hydrogen carbonate powder, and when sufficient gas is generated and foams, it is matched with this to quickly start polymerization and progress curing. . This suitable content condition is such that the curing agent is 0.5 to 100 parts by weight of the unsaturated polyester resin.
2.0 parts by weight, and the curing accelerator is used in an amount of 0.01 to 0.5 parts by weight. If the amount of this hardening agent is less than 0.5 parts by weight, curing will not start during the appropriate foaming process with the gas from the ammonium bicarbonate powder, while if it is more than 2.0 parts by weight, curing will not occur when gasification is sufficient and foaming does not occur. This is not preferable because foaming and curing cannot be matched. If the amount of curing accelerator used in combination is small (less than 0.01 part by weight), it will take a long time from the start of curing to completion; on the other hand, if the amount exceeds 0.5 part by weight, the curing speed will be too fast, resulting in uniform fine particles. This is not preferred because it is difficult to obtain a foamed product with fine cells. In the present invention, methyl ethyl ketone peroxide can be preferably used as a curing agent, and naphthenic cobalt is suitable as a curing accelerator to be used in combination with it. When used in combination with ammonium hydrogen carbonate, it has good molding workability and a uniform and fine shape. This is good because foaming of bubbles can be obtained. In the present invention, it is also possible to add an anhydrous organic acid as a compound that controls the thermal decomposition of ammonium bicarbonate powder. For example, acetic acid, acrylic acid, etc. can be used. Further, if necessary, fillers such as fibrous reinforcing materials, foam stabilizers, mold release agents, colorants, etc. can also be used as necessary. The three components, the ammonium bicarbonate powder, the curing agent, and the curing accelerator, may be added to the liquid unsaturated polyester resin at the same time, or only one component may be added to the unsaturated polyester resin in advance and then mixed. It is also possible to add and mix other two components separately mixed into the above mixture, or vice versa. As mentioned above, a mixture of three components added to an unsaturated polyester resin in the absence of water has a heating temperature of
It is foamed and cured under heating at 40 to 150°C, preferably 70 to 90°C. [Function of the Invention] The foaming method of the present invention involves thermally decomposing and gasifying ammonium hydrogen carbonate powder in the absence of water, and heating causes the viscosity of the unsaturated polyester resin to change to release gas at a time suitable for foaming. Unlike the second method, in which foaming is performed using gas generated by reaction with acid and water, the foaming conditions are set at a time when the curing effect of the unsaturated polyester resin is high. Can be matched. It is presumed that in the absence of water, an appropriate amount of curing agent and curing accelerator act to skillfully adjust the curing start time of the unsaturated polyester resin, resulting in a foam with uniform and fine cells. It is estimated to be. [Effects of the Invention] According to the present invention, by mixing ammonium bicarbonate powder, a curing agent, and a curing accelerator with an unsaturated polyester resin and heating the mixture in the absence of water,
The foaming and curing time can be significantly shortened, and a foam with uniform, fine cells can be obtained. As shown in the comparative example described later, even if ammonium hydrogen carbonate powder is used and only the curing agent is heated in the absence of water, it is difficult to obtain a foam with uniform fine cells unless a curing accelerator is used. Therefore, since the present invention is a method of efficiently foaming using an inexpensive foaming agent, it is possible to significantly reduce costs when implemented industrially. [Example] Examples of the present invention will be shown below, but the present invention is not limited thereto. Note that the number of parts indicates parts by weight. Examples 1 to 10 and Comparative Examples 1 to 4 Liquid unsaturated polyester resin (styrene 40%
Contains) per 100 parts, the specified amount of particle size shown in Table 1
150 ammonium bicarbonate powder of 10 μ or less, a specified amount of hardening agent, a specified amount of hardening accelerator, and 0.5 part of silicone oil are mixed and filled with the same amount of glass fiber.
It was poured into a formwork of ×150×10m/m. This was heated at the heating temperature shown in Table 1 to foam and harden it. The curing time from the start of heating to the completion of curing, the specific gravity of the obtained foam, and the external appearance of the foam are also listed in Table 1. In addition, the appearance (uniformity, fineness) of the foam is ◎...
The evaluation was shown as excellent, 〇...good, △...fair, and ×...unsatisfactory.

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Claims (1)

[Claims] 1. Ammonium hydrogen carbonate powder is mixed as a blowing agent into a liquid unsaturated polyester resin, organic peroxide is used as a hardening agent, and if necessary, a filler is also contained, and there is no water. A method for foaming an unsaturated polyester resin, characterized by foaming and curing under heating. 2. The method for foaming an unsaturated polyester resin according to claim 1, wherein the organic peroxide is methyl ethyl ketone peroxide. 3. The method for foaming an unsaturated polyester resin according to claims 1 and 2, wherein the curing accelerator is naphthenic cobalt.