CN1223272A - A kind of preparation method of acrylonitrile, styrene and polyacrylate graft copolymer - Google Patents

Abstract

The preparation method of AAS resin includes the following steps: firstly, making copolymerization of acrylate monomer and peroxidate with double bond to obtain the polyacrylate elastomer with peroxide lateral group; then, making said obtained polyacrylate elastomer, phenylethylene and acrylonitrile produce graft copolymerization reaction; changing the addition quantity of peroxide so as to regulate the graft density of polyacrylate elastomer; changing the addition quantity of graft monomer so as to regulate total grafting rate so that the controllable graft copolymerization is implemented. The grafting rate of the AAS resin obtained by said invented method can be up to 15%-40%, and Izod notch impact strength can be up to above 200J/m.

Description

A kind of preparation method of AAS resin

The invention belongs to the technical field of chemical industry and relates to a preparation method of controllable graft polymerization AAS resin.

The preparation technology of AAS resin (that is, graft copolymer of acrylonitrile, styrene and polyacrylate) is developed on the basis of ABS resin. It uses polyacrylate as the elastomer to replace the polybutadiene elastomer in the ABS resin, and is obtained through graft copolymerization with styrene and acrylonitrile. Since the polyacrylate elastomer does not contain double bonds, the weather resistance of AAS resin is much superior to that of ABS resin, and it has been widely used in many outdoor applications. However, because polyacrylate elastomers do not contain double bonds, it is difficult to initiate grafting during graft copolymerization with styrene and acrylonitrile, resulting in low grafting rate and poor impact toughness. In order to overcome this shortcoming, some people add monomers containing two double bonds for copolymerization during the preparation of polyacrylate elastomers, so that the obtained elastomers have a certain amount of double bonds to facilitate grafting. Some people add organic peroxides during graft polymerization to increase the grafting rate and crosslinking degree. There are also people who start with the grafting process conditions and use long-term continuous dripping of monomers to increase the grafting rate. But the mechanical property of commodity AAS resin is still not as good as ABS resin, the raising and control of grafting rate, and the improvement of material mechanical property, is a difficult point that people urgently hope to solve in the field of AAS resin preparation technology (referring to: Kohkame H, Shitara M, Tanno S, Muroi T, Journal of Applied Polymer Science, 46:1775-1784, 1992).

The object of the present invention is to provide a method for preparing AAS resin with excellent mechanical properties that can effectively increase the grafting ratio of the copolymer.

The basic steps of the method for preparing the AAS resin proposed by the present invention are as follows: when preparing the polyacrylate elastomer, add a peroxide with a double bond to the acrylate monomer. Below the decomposition temperature of the peroxide, through the mechanism of free radical polymerization, the copolymerization of the acrylate monomer and the peroxide monomer is carried out to obtain the polyacrylate elastomer with peroxy side groups. Then add graft monomers styrene and acrylonitrile, raise the temperature of the system to the decomposition temperature of the peroxy side group, make the peroxy side group decompose to generate macromolecular free radicals, and initiate the graft polymerization of styrene and acrylonitrile. By changing the amount of peroxide added, the density of grafted points of polyacrylate elastomer can be adjusted. The total grafting rate can be adjusted by changing the amount of grafting monomer added. Thus, controllable graft polymerization can be realized.

The acrylate monomer used to prepare the polyacrylate elastomer can be one or more of butyl acrylate, ethyl acrylate or other long-chain alkyl esters of acrylic acid.

The peroxides with double bonds used in the copolymerization have the following molecular structure:

R ₁ -OOR ₂

Wherein, R ₁ and R ₂ are two chemical groups, R ₁ contains a polymerizable double bond, and the part of R ₁ and R ₂ connected with the peroxy bond can be a carbonyl group or a tertiary carbon atom. Here are a few examples of such double bonded peroxides: CH ₂ =CHCH ₂ OC(O)-OO-tBu t-butylperoxyallyl carbonateCH ₂ =C(CH ₃ )C(O)OC ₂ H ₄ OC( O)-OO-tBu t-butylperoxymethacryloyloxyethyl carbonateCH ₂ =C(CH ₃ )C ₆ H ₆ C(CH ₃ )2-OO-tBu t-butyl-3-isopropenylcumyl peroxideCH ₃ CH(CH ₃ )O(O)CCH =CHC(O)-OO-tBu t-butylperoxyisopropyl formatarate

The copolymerization of acrylate monomers and peroxides with double bonds can be carried out in the presence of free radical initiators by using emulsion method, solution method or bulk method. The polymerization temperature should be more than 10°C lower than the temperature at which the decomposition half-life of the peroxy bond is 10 hours. If the polymerization temperature is too high, there will be too few side groups of peroxy bonds in the obtained polypropylene ester, which is unfavorable for subsequent grafting.

The ratio of acrylate monomer and the peroxide with double bond is (the sum of the two is 100) 95: 5～99.7: 0.3, and the peroxide with double bond is too little, then embodies the effect of the present invention is not obvious, too If there is too much, the density of grafting points will be too high when grafting with styrene and acrylonitrile later, and the impact toughness will become poor.

Graft polymerization can adopt emulsion method, solution method and bulk method. The grafting monomers used are mainly styrene and acrylonitrile, and one or more of the following monomers can also be added to adjust the performance: α-methylstyrene, methacrylonitrile, N-phenylmaleic acid imine, methyl methacrylate and more.

The ratio of the grafted monomer to the polyacrylate elastomer (the total amount is 100) is generally 10:90 to 80:20. If the amount of grafted monomers is too small, the grafting rate is too low, and the impact toughness of the product cannot be guaranteed. If it is too much, the grafting rate is too high, which is not good for performance, and the whole preparation process is not economical enough.

The temperature of the graft polymerization is generally 0°C to 60°C above the temperature at which the decomposition half-life of the peroxy bond is 10 hours. If the temperature of graft polymerization is too low, the polymerization time is too long. If the temperature is too high, the reaction is too intense and more homopolymers are formed.

The product obtained by graft copolymerization is AAS with high elastomer content, and then blended with commercial SAN resin (ie, a binary copolymer of styrene and acrylonitrile) through a screw extruder to obtain a practical AAS resin. According to different requirements on product performance, the content of polypropylene ester elastomer in the final blended product can be 14% to 25%. The higher the elastomer content, the higher the impact resistance, but the worse the rigidity, heat resistance and processability.

Various additives can be added as needed during screw extrusion blending. Such as antioxidants, UV absorbers, antistatic agents, flame retardants, lubricants and pigments, etc.

The grafting rate of the AAS resin obtained by the method of the invention can reach 15%-40%, and can be controlled according to needs.

When the content of polyacrylate elastomer is 20%, the notched Izod impact strength can reach more than 200J/m.

The test method of the grafting rate is as follows: Take 0.5 grams of the grafted polymerization product, disperse it in 25 milliliters of acetone, place it on an electromagnetic stirring table, stir and dissolve at room temperature for 2 hours. Take 2 ml of the suspension and separate it by centrifugal sedimentation in a centrifuge at 12,000 rpm. After the precipitate is washed and separated three times with acetone, it is analyzed by infrared spectroscopy. Calculate the grafting ratio from the standard curve. The graft ratio is defined as the ratio of the weight of grafted styrene/acrylonitrile copolymer to the weight of polyacrylate elastomer.

The test method of the impact strength of AAS resin is as follows: AAS resin is processed into a test strip of 63.5×3.17 mm by injection molding method, and a "V"-shaped notch is processed by a milling machine, and the impact strength of the Izod beam is tested according to GB1843. Example 1:

Butyl acrylate, ethylene glycol diacrylate and peroxide 1-(2-tert-butylperoxyisopropyl)-3-isopropenylbenzene are mixed in a weight ratio of 97/2/1 to obtain a mixed unit body. Add 200 parts of deionized water, 1.5 parts of emulsifier sodium lauryl sulfate and 0.3 parts of initiator potassium persulfate into a three-necked bottle with a condenser, stir under a nitrogen blanket and raise the temperature to 70 ° C, mix 100 parts The monomer was continuously dropped into the three-necked bottle within 4 hours, and then maintained at 70° C. for 2 hours to obtain a polyacrylate elastomer latex with a solid content of 32% and a particle size of 0.20 μm.

Add 120 parts of polyacrylate elastomer gel holes, 220 parts of deionized water, 44 parts of styrene, 16 parts of acrylonitrile, and 0.2 parts of sodium lauryl sulfate into the autoclave. Sealed after nitrogen replacement, stirred and heated to 120°C for 4 hours, the conversion rate reached 95%. Cool and discharge, coagulate with magnesium sulfate, wash with water, and dry in a blast oven at 70°C to obtain graft powder with high elastomer content. After analysis, the graft rate is 23%.

With 47.6 parts of grafting powder, 0.5 part of antioxidant B-215, 52.4 parts of SAN resin (the binary copolymer of styrene and acrylonitrile produced by Lanhua Company, model HF), 0.4 part of EBS (bis stearamide) Mix evenly, extrude and granulate with a twin-screw extruder. After testing, the notched Izod impact strength of the AAS resin is 214J/m. Example 2:

The polybutyl acrylate elastomer emulsion of Example 1 was used for graft copolymerization. 155 parts of the elastomer emulsion, 195 parts of deionized water, 0.2 parts of sodium lauryl sulfate, 36.5 parts of styrene and 13.5 parts of acrylonitrile were added. All the other steps are the same as in Example 1. The elastomer content was also diluted to 20% with SAN when blending, resulting in an impact strength of 204 J/m. Comparative example 1:

Prepare polybutyl acrylate elastomer emulsion in a manner similar to Example 1, except that D120 is not added during polymerization, only butyl acrylate and ethylene glycol diacrylate (98: 2) are added, and the solid content of the emulsion obtained is 32.5%. Particle size 0.30μ. During graft copolymerization, the formula is similar to that of Example 1, but adding 0.8 parts of initiator potassium persulfate, reacting at 80°C for 5 hours, the conversion rate is 95%, coagulation, washing, drying and blending in the same way, the impact strength is only Reach 15J/m, the grafting rate is lower than 7% Comparative Example 2:

A polybutylacrylate elastomer emulsion was prepared in a manner similar to Example 1. The ratio of butyl acrylate, ethylene glycol diacrylate and D120 was changed to 98:2:0.2. As a result, the solid content of the emulsion measured was 32.5%, and the particle size was 0.22μ. The conditions of graft copolymerization are also the same as in Example 1, but the conversion rate only reaches 80%. Coagulate, wash and dry in the same way to obtain graft powder. When blending, the ratio of graft powder to SAN was 47.6:52.4, so that the content of the elastomer in the blend was kept at 20%, which was the same as in Example 1. As a result, due to the low content of D120, the impact strength only reached 18J/m, and the grafting rate of graft powder was lower than 8%.

Claims (8)

1, a kind of method for preparing AAS resin when it is characterized in that preparing the polyacrylate elastomerics, adds the superoxide of being with two keys, its molecular architecture: R to acrylate monomer ₁-O-O-R ₂, R here ₁And R ₂Be two kinds of chemical groups, wherein R ₁Contain polymerisable double bonds, R ₁And R ₂In the part that links to each other with peroxide bridge be carbonyl or tertiary carbon atom, acrylate monomer is 95: 5 to 99.7: 0.3 with the part by weight of the superoxide of the two keys of band, below the decomposition temperature of this superoxide, mechanism by radical polymerization, carry out acrylate monomer and the monomeric copolymerization of this superoxide, obtain polyacrylate elastomer with the peroxide side group; Add vinylbenzene and acrylonitrile monemer then, system temperature is elevated to the decomposition temperature of peroxide side group, the peroxide side group is decomposed generate macromolecular radical, cause the graft polymerization of vinylbenzene and vinyl cyanide; Change the add-on of superoxide, regulate the grafting site density of polyacrylate elastomer, change the add-on of grafted monomer, regulate total percentage of grafting, thereby realize controllable graft polymerization, the part by weight of grafted monomer and polyacrylate elastomer is 10: 90 to 80: 20.

2,, it is characterized in that used acrylate monomer is one or more of ethyl propenoate, butyl acrylate or acrylic acid other long-chain alkyl groupses according to the described method for preparing AAS resin of claim 1.

3, the method for preparing AAS resin according to claim 2, it is that 10 hours temperature is low more than 10 ℃ that the temperature that it is characterized in that acrylate monomer and the superoxide copolymerization of the two keys of band decomposed for half rate phase than peroxide bridge.

4, the method for preparing AAS resin according to claim 3, it is characterized in that adding in addition following monomeric one or more: alpha-methyl styrene, methacrylonitrile, methyl methacrylate, N-phenylmaleimide.

5, the method for preparing AAS resin according to claim 4, the temperature that it is characterized in that graft polymerization more than 10 hours temperature of peroxide bridge half life of decomposition 0 ℃ to 60 ℃.

6. according to the claim 5 described methods that prepare AAS resin, it is characterized in that adding in addition monomeric down one or more: alpha-methyl styrene, methacrylonitrile methyl methacrylate, N-phenylmaleimide.

7. according to the claim 6 described methods that prepare AAS resin, the ratio that it is characterized in that grafted monomer and polyacrylate elastomer is 10: 90 to 80: 20.

8. according to the claim 7 described methods that prepare AAS resin, the temperature that it is characterized in that graft polymerization more than 10 hours temperature of peroxide bridge half life of decomposition 0 ℃ to 60 ℃.