JPH051296B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous butadiene copolymer dispersion having extremely excellent resistance to heat deterioration. More specifically, the present invention relates to a novel aqueous polymer dispersion that exhibits very little thermochromic discoloration in high-temperature air and almost no thermal deterioration. Conventionally, latexes such as styrene-butadiene copolymer (SBR), acrylonitrile-butadiene copolymer (NBR), and methyl methacrylate-butadiene copolymer (MBR) have been commercialized as aqueous butadiene copolymer polymer dispersions. In general, these butadiene copolymer polymer aqueous dispersions have unsaturated bonds in their molecular chains, so these films yellow, soften, or harden when exposed to ozone, oxygen, heat, light, etc. This causes a deterioration phenomenon and a significant decrease in the properties of the polymer.
This is often a practical problem. In order to prevent such deterioration, various antioxidants such as phenolic and amine antioxidants have traditionally been added to aqueous polymer dispersions, and although they have been shown to be quite effective under relatively moderate temperature conditions, It is not very effective when exposed for a long time, which is a big problem in practice. For example, styrene-butadiene copolymer has traditionally been used as a backing agent for carpets, but in recent years there has been an increase in demand for it as a backing agent for electric carpets for heating. It is required that there is no deterioration even when exposed. However, simply adding various antioxidants to the styrene-butadiene copolymer does not provide the practically necessary heat deterioration resistance. As a result of intensive research by the present inventors in order to provide a butadiene copolymer polymer aqueous dispersion that exhibits excellent heat deterioration resistance and heat discoloration resistance when used at high temperatures,
Discovered that a film of an aqueous butadiene copolymer dispersion obtained by emulsion polymerization of a monomer mixture with a specific composition in the presence of a specific antioxidant has extremely excellent heat deterioration resistance, and completed the present invention. I came to the conclusion. That is, in the present invention, in the presence of 0.1 to 2.0 parts by weight of an antioxidant comprising a diphenylamine derivative and a phenol derivative in a weight ratio of 70/30 to 30/70, butadiene is added in an amount of 10 to 90% by weight based on the total monomers. and an ethylenically unsaturated monomer 90 copolymerizable with butadiene containing one or more ethylenically unsaturated dicarboxylic acids in an amount of 1 to 10% by weight based on the total monomers containing butadiene.
It can be summarized as an aqueous butadiene copolymer dispersion having extremely excellent heat deterioration resistance and obtained by emulsion polymerization of 100 parts by weight of a monomer mixture consisting of ~10% by weight. The reason why butadiene copolymer polymers tend to deteriorate thermally is the residual unsaturated bonds in the polymer caused by butadiene. Therefore, as the butadiene content increases, the heat deterioration resistance tends to decrease, but when the butadiene content in the total monomer is less than 10% by weight, the heat deterioration due to butadiene is slight;
In practice, sufficient effects can be obtained by adding only the antioxidant. However, if the butadiene content is 10% by weight or more, thermal deterioration is significant, and even if an antioxidant is used in combination, no significant improvement effect can be obtained, and currently it cannot be used in applications that require heat resistance. It is. On the other hand, if the butadiene content exceeds 90% by weight, the polymerization rate decreases and the polymerization reaction does not proceed in the presence of the antioxidant in the present invention, resulting in poor practicality. Examples of the ethylenically unsaturated monomer in the present invention include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, butyl methacrylate, butyl acrylate, butyl methacrylate, pentyl acrylate, Examples include pentyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, octyl acrylate, octyl methacrylate, octadecyl acrylate, and octadecyl methacrylate. Acrylic acid alkyl ester and methacrylic acid alkyl ester styrene, α-methylstyrene, vinyltoluene, chlorstyrene, 2,4
- Ethylenically unsaturated aromatic monomers such as dibromustyrene, unsaturated nitriles such as acrylonitrile and methacrylonitrile, vinyl esters such as vinyl acetate and vinyl propionate, acrylic acid, methacrylic acid, itaconic acid, ethylenically unsaturated carboxylic acids such as fumaric acid, vinylidene chloride,
vinylidene halides such as vinylidene bromide, hydroxyalkyl esters of ethylenically unsaturated carboxylic acids such as 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, etc.
Glycidyl esters of ethylenically unsaturated carboxylic acids such as glycidyl acrylate, glycidyl metharylate, etc. and acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-butoxymethylacrylamide, diacetone acrylamide, etc. with butadiene. Any polymerizable monomer can be used, but it must always contain 1 to 10% by weight of one or more ethylenically unsaturated dicarboxylic acids based on the total monomers. This is the most distinctive feature of the present invention, in which heat deterioration resistance is significantly improved by copolymerizing butadiene, ethylenically unsaturated dicarboxylic acid, and other copolymerizable monomers in the presence of a specific antioxidant. It is. Ethylenically unsaturated dicarboxylic acids used in the present invention include itaconic acid, fumaric acid, maleic anhydride, crotonic acid, and the like. These are used in a range of 1 to 10% by weight based on the total monomer mixture, but if it is less than 1.0% by weight, the polymerization rate will be very slow and a large amount of coagulum will be formed in the dispersion after polymerization. Furthermore, there is no effect of improving heat deterioration resistance. Moreover, if it is used in an amount exceeding 10% by weight, the viscosity of the dispersion increases, causing a practical problem. The antioxidants used in the present invention include diphenylamine, para-aminodiphenylamine, N-isopropylamine diphenylamine,
N-4-anilinophenyl acrylic acid amide, N
-4-anilinophenyl methacrylic acid amide,
Examples include diphenylamine derivatives such as N-4-anilinophenylbenzoic acid amide. Also phenol, and 2,6-ditertiary
Examples include phenol derivatives such as butylphenol, 2,6-di-tertiary-butylcresol, and styrenated phenol. In the present invention, the weight ratio of phenol derivative A and diphenylamine derivative B is A/B=70/30.
It is preferable to use them together in a range of ~30/70, and 0.1 to 2.0 parts by weight per 100 parts by weight of the monomer, but if it is less than 0.1 parts by weight, excellent heat deterioration resistance will not be obtained. Moreover, if it is used in an amount exceeding 2.0 parts by weight, the polymerization rate becomes extremely slow and a large amount of coagulum is formed in the dispersion after polymerization. The aqueous polymer dispersion in the present invention is prepared under conditions of ordinary emulsion polymerization. For example, a monomer mixture is emulsified and dispersed in water using an emulsifier in the presence of the above antioxidant, and a free radical generating catalyst such as KPS (K ₂ S ₂ O ₈ ), APS ((NH ₄ ) ₂ S ₂ O ₈ ) Emulsion polymerization may be carried out preferably at 50°C to 70°C using an aqueous catalyst such as hydrogen peroxide, or an oily catalyst such as t-butyl hydroperoxide or cumene hydroperoxide. Furthermore, the present invention does not require the use of additives commonly used in emulsion polymerization, such as chain transfer agents, ethylenediaminetetraacetic acid for polymerization stabilization and buffering effects, or alkaline substances for pH adjustment. I can't help it.
Note that there is no problem in adding a step of concentration or removal of unreacted monomers to the aqueous copolymer dispersion after emulsion polymerization. The dried film of the aqueous polymer dispersion of the present invention obtained in this way has excellent heat deterioration resistance, and there is almost no deterioration in the physical properties of the film even when exposed to high-temperature air for a long time, and there is almost no thermal discoloration. It is. Therefore, it is excellent as an adhesive for areas subject to high heat, such as a backing agent for electric carpets, and as a paper treatment agent. Next, the present invention will be explained in more detail with reference to Examples. Note that "parts" and "%" in each example are based on weight. Example 1 120 parts of ion-exchanged water, 2 parts of sodium alkylbenzenesulfonate (Neoperex F-25, Kao Soap Products) as an active ingredient, and 0.5 part of tert-dodecyl mercaptan were placed in a nitrogen-substituted autoclave equipped with a stirrer.Table 2 100 parts of monomers with the compositions shown in A, B, and C of Table 2 and antioxidants with the compositions shown in Table 2 are added, and 0.5 part of potassium persulfate was added, and the mixture was heated at 60°C for 12 hours with stirring. After emulsion polymerization, unreacted monomers were removed by steam distillation, concentration was performed, and pH was adjusted by adding potassium hydroxide to obtain a latex with a solid content of 50% and a pH of 8.5. All of them were polymerized to a polymerization rate of 98% or more, and stable latexes A, B, and C were obtained without aggregates. Comparative Example 1 Emulsion polymerization was carried out in the same manner as in Example 1 except that the monomer composition and antioxidant composition were as shown in D, E, F, G, H, and I in Table 2, and latex D, E, F, G, H, and I were obtained. In Latex I, the antioxidant was prepared in advance as an aqueous dispersion having the composition shown in Table 1, and after the polymerization reaction was completed, hindered phenol and diphenylamine were added at 0.6 parts and 0.4 parts, respectively, per 100 parts of the solid content of the latex. It was added so that

【table】

[Table] Example 2 Latexes A to I obtained in Example 1 and Comparative Example 1
were cast onto glass plates to a dry film thickness of 0.5 to 0.7 mm, and air-dried at 20°C for 48 hours to obtain films, and films obtained by further heating at 180°C in a gear oven for 5 hours. Punch out the film with a JIS No. 1 dumbbell to create a specimen, and pull it with Tensilon at a speed of 500 mm/mm.
The strength and elongation of the film was measured under these conditions, and the state of thermal deterioration was compared. The measurement results are shown in Table 3. The coatings of latexes A to C of the examples of the present invention show very little change in strength and elongation when dried only naturally or when heated in a gear oven, and have excellent heat deterioration resistance, whereas the latexes of the comparative examples When all of D to I were heated in a gear oven, the modulus and tensile strength were higher and the elongation was significantly lower than that of the films that were only air-dried. This is because the film hardens due to oxidation and loses its original rubber elasticity and flexibility, indicating thermal deterioration.

【table】

[Table] Example 3 Latexes A to I obtained in Example 1 and Comparative Example 1
Each compound for carpet backing having the composition shown in Table 4 was prepared using
The degree of discoloration of the film and the flexibility of the film were compared. The results are shown in Table 5. The films of the compounds using latexes A to C of the examples of the present invention show almost no discoloration or hardening of the film when heated in a gear oven compared to when only air-dried. It can be seen that the heat deterioration resistance is very excellent. In contrast,
The films of the compounds using latexes D to I of comparative examples showed significant thermal discoloration and hardening of the films, and thermal deterioration was progressing.

【table】

[Table] Example 4 The same method as in Example 1 except that the monomer composition, antioxidant composition, reaction conditions, mercaptan amount, and potassium persulfate amount were as described in J, K, and L of Table 6. Emulsion polymerization was carried out using steam distillation to remove unreacted monomers, concentration, and pH adjustment by adding potassium hydroxide to obtain stable latexes J, K, and L having a solid content of 50% and a pH of 7.

【table】

[Table] Example 5 Using latexes J, K, and L obtained in Example 4,
Under the same conditions as in Example 2, the strength and elongation of the air-dried film and the gear oven-heated film of each latex were measured. The results were as shown in Table 7.

【table】

Claims (1)

[Claims] 1. Consisting of diphenylamine derivative A and phenol derivative B, the weight ratio of which is A/B = 70/30.
10 to 90% by weight of butadiene in the presence of 0.1 to 2.0 parts by weight of an antioxidant that is ~30/70 and 1% to the total monomer mixture containing butadiene.
Emulsion polymerization of 100 parts by weight of a monomer mixture consisting of 90 to 10% by weight of an ethylenically unsaturated monomer copolymerizable with butadiene containing 1 to 10% by weight of one or more ethylenically unsaturated dicarboxylic acids. Heat-resistant deterioration polymer aqueous dispersion obtained by