KR820002027B1 - Method for improving color and impact strength of nitrile polymers - Google Patents

Abstract

The color and impact strength of nitrile polymers, prepared by polymn. of an olefinically unsatd. nitrile with a monovinyl monomer in the presence of a rubber, were improved by heating the polymer to a plastic state in the absence of O and in presence of an inert gas. Thus, an acrylonitrile-rubber-vinyl compd. latex, coagulated and formed into strands was pelletized by screw extrusion in the presence of CO2. The product had Izod impact strength 2.57kg/cm2, yellowness index 28.

Description

How to improve the color and impact strength of nitrile polymers

The present invention improves the color and impact strength of a polymer by heating a nitrile polymer produced by polymerizing a preformed rubber component of a polymer consisting of an olefinically unsaturated nitrile and at least 50% by weight of nitrile in the presence of oxygen and an inert gas. It is about a method.

The polymer may be made in various forms, namely dense pellets (lenses), or film sheets, pipes, bottles or injection molded articles, or blow molded articles.

Typically, the coagulated latex formed by the polymerization should be prepared before the end purpose is achieved. Its manufacturing methods include densification of polymer strands into pellets, compounding or mixing resins with various additives to advance physical properties, compacting into pellets or final products, and injection blow molding. There are ways to make it.

Typically, in the manufacturing process, the polymer is heated to a plastic state. Improved yellowness index and impact strength can be obtained by substituting oxygen with inert gas during heating and plasticization.

The present invention also provides a method of making a product from a polymer produced by densifying a polymer strand and a product from a non-dense polymer.

Dry coagulated latex formed by polymerization is usually densified before final use. This densification improves the physical quality of the polymer and removes volatile components to provide an easy-to-use form. Densification is carried out in the extruder. The latex strand is fed to a screw or other type of extruder. External heating or conductive heat from screws or cylinders is used to achieve the plasticity required for extrusion. By such densification, pellets or lenticular products are obtained.

Densified pellets are used to form the final product. These products include sheets, pipes and bottles. At this time, the pellet is heated again to plasticize. The plasticized polymer is extruded or injection blow molded into final form. The final product can also be made directly from latex strands without intermediate densification.

In the prior art, air is injected into the polymer during heating and plasticization of the strands or pellets. The polymer is plasticized with an increase in temperature, so it condenses more tightly and the air is forced out.

However, oxygen in the air attacks the polymer and adversely affects it. Replacing oxygen with an inert gas in the heating and plasticizing steps improves the properties such as the yellowness index and impact strength of the polymer. In addition, the same quality as in the prior art is greatly increased in its production.

As the inert gas used in place of oxygen in this step, any gas inert to the polymer can be used. Preferred are nitrogen and carbon dioxide.

Examples of the nitrile polymer belonging to the present invention include an interpolymer prepared by polymerizing a resinous polymer and most monocyclic nitriles (such as acrylonitrile) and another monovinyl monomer component copolymerizable with the nitrile in an aqueous medium. This copolymerization can be carried out in the presence of a preformed diene rubber which may be a homopolymer or a copolymer of conjugated diene monomer.

Olefinically unsaturated nitriles useful in the present invention include α, β-olefinically unsaturated mononitriles of the formula:

R in the formula is hydrogen, lower alkyl of 1 to 4 carbon atoms, or halogen. Such compounds include acrylonitrile, alphachloroacrylonitrile, alphafluoroacrylonitrile, methacrylonitrile, etaacrylonitrile, and the like. Most preferred olefinically unsaturated nitriles are acrylonitrile, methacrylonitrile and mixtures thereof.

Another monovinyl monomer component that can be copolymerized with olefinically unsaturated nitriles useful in the present invention includes one or more esters of olefinically unsaturated carboxylic acids, vinyl esters, vinyl ethers, alpha-olefins, vinylaromatic monomers and the like.

The ester of the olefinically unsaturated carboxylic acid has the following structural formula.

In the above structural formula, R ₁ is hydrogen, alkyl group having 1 to 4 carbon atoms, or halogen, R ₂ represents an alkyl group having 1 to 6 carbon atoms.

Compounds of this type include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate and hexane acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl Methacrylate and hexane methacryl, methyl alpha-chloroacrylate, ethyl alpha chloroacrylate and the like. Most preferred in the present invention is to have a carbon number of 4 to 10 or less and have the following structural formula.

R 'and R' 'in the above structural formula are alkyl having 1 to 7 carbon atoms and particularly preferred isobutylene, 2-methylbutene-1,2-methylpentene-1,2-methylhepten-1,2-methyloctene- Isobutylene such as 1,2-ethylbutene-1,2-propylpentene-1 and the like is most preferably isobutylene.

Vinyl ethers include methyl vinyl ether, ethyl vinyl ether, propyl ether, butyl vinyl ether, methyl isopropenyl ether and ethyl isopropenyl ether. Most preferred are methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether and butyl vinyl ether.

Vinyl esters include vinyl acetate, vinyl propionate and vinyl butyrate. Most preferred is vinyl acetate.

Vinylaromatic monomers include styrene, alpha-methylstyrene, vinyltoluene, vinylxylene, isopropylstyrene (0-, m- and p-isopropylstyrene and mixtures thereof).

Conjugated diene monomers useful in the present invention include butadiene-1,3, isoprene, chloroprene, bromoprene, cyanoprene, 2,3-dimethyl-butadiene-1,3,2-ethylbutadiene-1,3, 2,3 Diethyl butadiene-1,3 and the like. Most preferably used in the present invention are butadiene and isoprene because they are easy to prepare and have excellent copolymerizability.

Polymerization agents and methods for the preparation thereof which are particularly used in the present invention are described in US Pat. Nos. 3,426,102, 3,586,737 and 3,763,278.

Polymerizers useful in the present invention include 100 parts by weight of (A) a nitrile having at least 50% by weight of the following structural formula:

Where R is as above.

(B) 50% by weight of (A) and (B) gross weight

(1) Ester of the following structural formula (R ₁ and R ₂ are the same as above).

(2) Alpha-olefins of the following structural formulae (R 'and R' 'are as above).

(3) Vinyl ether selected from methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether and butyl vinyl ether

(4) vinyl acetate and

(5) styrene

At least one selected from among (C) butadiene and isoprene is selected from diene monomer and styrene, and nitrile of the following structural formula (R is as described above):

Prepared by polymerization in the presence of a rubbery polymer of the selected comonomer, which contains 50 to 100% by weight of polymerized conjugated diene and 0 to 50% by weight of comonomer.

Preferably, component (A) should be present in the range of 60 to 90% by weight of the total weight of (A) and (B), and the rubbery polymer (C) should contain at least 50% by weight of conjugated diene, preferably 60 To 90% by weight of conjugated diene.

The polymerizable composition of the present invention is prepared by using general known polymerization techniques such as bulk polymerization, solution polymerization, emulsion or suspension synthesis techniques and by adding monomers and other components in batches, continuously or intermittently. This polymerization is preferably carried out by an aqueous emulsion or suspension technique without oxygen molecules at 0 to 100 ° C. in the presence of an emulsifier, a molecular weight modifier, and a free radical polymerization initiator. It is also preferable that the monomer is copolymerized in the presence of an emulsion or suspension of the exemplified rubber. The product by aqueous emulsion polymerization is latex type, and the copolymer can be recovered from the latex by a suitable method such as coagulation with an electrolyte or a solvent and freezing.

Physical properties improved by the present invention, the impact strength was measured by a scaled Izod test recorded in ASTM D256 "impact resistance of plastics and electrical insulating materials". The results are in ft tb / inch scales. The higher the value, the greater the impact strength of the polymer. ·

The yellowness index of plastics can be seen in ASTM D1925-70, "Yellowness Index of Plastics". The lower the index, the lower the yellowness of the polymer.

Other physical properties associated with this resin are turbidity and light transmittance. This value is determined by ASTM D1003, "Standard Method for Measuring Turbidity and Light Transmittance of Transparent Plastics".

The following examples illustrate the invention in detail.

Example 1

Acrylonitrile-rubber latex is prepared according to the methods described in US Pat. Nos. 3,426,102 and 3,586,737 and the polymer is recovered from the latex by coagulation to form a strand.

Densify using a screw extruder and pellet the strands. The extrusion screw consists of two stages. The speed of the screw is about 100 rpm. The pellets are collected, directly compressed (D.C) and milled (M.M) into plaques and then tested for yellowness index, light transmittance, turbidity and Izod impact strength.

Example 2

inch O.D. 튜브를 끼어 넣는다. 실시예 1과 동일한 스트렌드, 압출기 및 스크루 속도의 사용하에, 21ps에서 튜브를 통하여 질소를 8분동안 공급하여 공기를 신선하게 한후 펠릿화시킨다. 질소의 공급을 계속하는 동알 펠릿을 수집하고 이 펠릿을 플라크로 만든 후 실시예 1과 같이 시험한다.In order to know the effectiveness of nitrogen discharge,

Insert the inch OD tube. Using the same strands, extruders and screw speeds as in Example 1, the air was freshened and pelletized by feeding nitrogen for 8 minutes through the tube at 21 ps. Collect copper pellets that continue to be supplied with nitrogen, make the pellets plaque and test as in Example 1.

Example 3

Example 2 is repeated but carbon dioxide is discharged instead of nitrogen. The carbon dioxide is fed through a tube at 33 psi for 8 minutes to freshen the air, and then the pellets are collected while continuously supplying carbon dioxide. The collected pellets are made into plaques and tested as in Example 1.

Table 1 shows the beneficial effects obtained by removing oxygen during the heating and plasticization process. "D.C." And "M.M." refer to direct compression and grinding and molding, respectively.

As previously seen, the present invention has greatly improved the physical properties of the pellets. An important improvement shown in Table 1 is that when using the present invention a light transmittance of 2 to 3% is obtained. In the case where the strand must be of a specific color, the higher the light transmittance%, the less color should be added for the yellowness.

The same nitrile polymer strand is used to form pellets in the presence of air and nitrogen. Pellets are formed into 20OZ bottles and the drop height is determined. It can be seen that the bottle prepared using the pelletized polymer in the air has a drop height of 6.1 ft and the bottle formed from the pelletized polymer in the presence of nitrogen has a significantly increased drop height of 11.5 ft.

An additional benefit of the present invention is that it increases production. In the case of densification using the same extruder, the use of nitrogen discharge increases the densification rate by 20% and maintains the desired yellowness and Izod number.

TABLE 1 Properties of polymers improved using inert gas

Claims (1)

A nitrile polymer having at least 50 weights of nitrile, prepared by condensing an olefinically unsaturated nitrile and a rubber element already formed, is heated in a plastic state in the presence of an oxygen element and an inert gas, thereby reducing the color and impact strength of the nitrile polymer. How to improve.