Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-02-01
2004-05-04
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
active
06730741
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a processing aid for vinyl chloride based resin and a vinyl chloride based resin composition using the same, and more particularly to a processing aid for calender molding, which provides an effect of promoting gelation during calender molding of vinyl chloride based resin without giving damages to properties that the vinyl chloride based resin originally has, and can eliminate generation of ungelled products of a calendar sheet that are problematic in calender molding and flow marks that can hardly be eliminated by conventional processing aids, and also improves releasability of sheets from roll metal surfaces during calender molding, a vinyl chloride based resin composition for calender molding using the same, and a method of producing moldings using the same.
BACKGROUND ART
Vinyl chloride based resin are excellent in various kinds of physical properties and chemical properties, and are widely used for various kinds of products such as films, sheets, bottles, building materials, floor materials and wire coatings. However, for vinyl chloride based resin, the molding range is limited because the molding temperature is close to the thermal cracking temperature, and it is difficult to obtain uniform molten material from powder quickly by kneading operations and the like because the speed of gelation is low, often resulting in deteriorated surfaces of molten material. Many techniques aiming at overcoming these problems are known. They include, for example, addition of plasticizers, and copolymerization of vinyl chloride resin with other monomer. However, addition of plasticizers causes problems such as vaporization and escaping of plasticizers, and may compromise physical properties of final moldings. In the method using coplymerization of vinyl chloride resin with other monomer, the amount of monomer to be copolymerized should be limited for carrying out the copolymerization without giving no damages to the original properties of vinyl chloride resin, and if the amount thereof is too large, the physical properties of final moldings may be deteriorated as in the case of addition of platicizers.
On the other hand, for the purpose of improving so called processability such that gelation of resin is promoted during molding of vinyl chloride, the smoothness of the surface of the moldings is maintained even in long time molding, and the gloss of the surface Is kept constant, some of copolymers compatible with vinyl chloride resin are considered as processing aids, and method of blending these copolymers as processing aids. All of them are copolymers having methyl methacrylate as a main component. For vinyl chloride resins with these copolymers blended therein, the gelation speed is high and secondary processability is significantly improved, but there are disadvantages leading to degradation of commercial values of final moldings, for example generation of ungelled products due to their poor dispersion.
Then, as a method for enhancing the gelation speed of vinyl chloride resin, and curbing the generation of ungelled products due to poor dispersion of added processing aids, a vinyl chloride based resin composition is proposed in which a multi-stage copolymer comprising polymethyl methacrylate and a copolymer of a monomer superior in amount selected from the group consisting of acrylates and methacrylates other than methylmethacrylate and methylmethacrylate inferior in amount, or a polymer mixture with these polymers blended in latex conditions, or a multi-stage polymer comprising a copolymer obtained from methyl methacrylate superior in amount and a monomer inferior in amount selected from the group consisting of acrylates and methacrylates other than methyl methacrylate, and a copolymer obtained from methyl methacrylate inferior in amount and a monomer superior in amount selected from the group of consisting of acrylates and methacrylates other than methyl methacrylate, or a polymer mixture with these polymers blended in latex conditions are blended as processing aids (Japanese Patent Publication No. 52-49020, Japanese Patent Publication No. 53-2898).
In addition, it is also proposed that a multi-stage polymer with the diameter of particles of latex defined is used when a processing aid is prepared by emulsion polymerization (See Japanese Patent No. 2515014).
Vinyl chloride based resin compositions with a processing aid comprising such specific copolymers described in the above publication have improved properties in terms of generation of ungelled products and secondary processability.
For improving secondary processability while promoting gelation, however, the molecular weight of the processing aid should be large. For this reason, the melting viscosity of the resin composition during molding is increased, thus rising a disadvantage that flow marks are generated on the surface of calendar sheets during calender molding, resulting in degradation of the commercial value of moldings at the same time.
For the purpose of improving the above described problems, a vinyl chloride based resin composition is proposed in which a copolymer comprising methyl methacrylate and specific methacrylate is blended as a processing aid (See Japanese Patent No. 2813248).
On the other hand, the copolymer having methyl methacrylate as a main component also has a disadvantage that its stickiness to metal surfaces is essentially high, which leads to poor releasability of sheets from the metallic surface of a roll.
For the purpose of improving the releasability of sheets from the metallic surface of a roll in calender molding, use of various kinds of lubricants in combination is considered, but upper limits should be imposed on the amount of these lubricants to be used in terms of maintenance of the physical properties of vinyl chloride based resin compositions, and even within the proper range of usage amounts, lack of long-term releasability of sheets, the bloom to the surface of a final moldings or deposition of lubricants to the metallic surface of the roll during calender molding is caused, and thus it cannot provide a universal solution.
In recent years, in calender-molding of vinyl chloride resin, enhancement of production speed to reduce molding time together with the scale-up of molders is promoted in order to improve producibility. In association with the enhancement of the speed of calender molding, a large number of ungelled products and flow marks are generated on the sheet molded by calender molding, leading to deterioration of appearance and quality of final moldings, and thus techniques to improve this situation are required. In addition, techniques to further improve releasability of sheets from the metallic surface of the roll are also required.
DISCLOSURE OF THE INVENTION
An object of the present invention is to fulfill the above described requirements. That is, an object of the present invention is to provide, under a high speed calender molding condition of a vinyl chloride based resin, a processing aid for calender molding that reduces generation of ungelled products and flow marks on sheets leading to degradation of commercial values of final moldings, and improves releasability of sheets from the metallic surface of a roll, a vinyl chloride based composition for calender molding using the processing aid.
As a result of making vigorous considerations to solve the above described problems, the inventors have found that a processing aid comprising two types of polymers different in functionality, namely a copolymer (A) and a copolymer (B) is blended in vinyl chloride resin, thereby making it possible to reduce ungelled products and flow marks in calender-molding, and improve the releasability of sheets from the metallic surface of a roll, and thus completed the present invention.
That is, the gists of the present invention are
(1) a processing aid comprising:
a copolymer (A) whose mean weight molecular weight (Mw) measured with gel permeation chromatography is in the range of from 700,000 to 2,000,000, and molecular weight distribution (Mw
Honda Souichiro
Nakata Akira
Tsuchibe Ken
Buttner David J.
Mitsubishi Rayon Co. Ltd.
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