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
1990-10-15
2001-08-21
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S356000, C526S200000, C526S224000, C526S344000
Reexamination Certificate
active
06277922
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a low color chlorinated polyvinyl chloride (CPVC) composition as well as the preparation thereof. The low color is due to the type of polymerization additive employed in the polymerization of vinyl chloride to obtain polyvinyl chloride (PVC). The typical polymerization additives used in the making of PVC were found to cause discolorated CPVC products. It has been found that polyvinyl alcohol in general and especially low to medium hydrolysis polyvinyl alcohol are the major contributors to the discoloration of CPVC.
BACKGROUND
U.S. Pat. No. 4,612,345 (Hess, Sep. 16, 1986) relates to suspending agents of the hydroxypropyl methyl cellulose type and to a process for preparing vinyl chloride polymers by suspension polymerization of vinyl chloride wherein hydroxypropyl methyl cellulose ethers are used as suspending agents.
This patent provides new suspending agents of the hydroxypropyl methyl cellulose type for suspension polymerization of vinyl chloride which do not have the deficiencies of the known suspending agents of this type. This reference also provides new suspending agents of the hydroxypropyl methyl cellulose type for suspension polymerization of vinyl chloride which suspending agents are useful for increasing or controlling the porosity of the produced polyvinyl chloride particles.
U.S. Pat. No. 4,797,458 (Sharaby, Jan. 10, 1989) relates to polymers of vinyl halides having low molecular weight, good particle characteristics and improved melt flow. The polymers are made by aqueous polymerization utilizing an effective amount of a mercaptan as a chain transfer agent, wherein the mercaptan chain transfer agent is mixed with at least one material which is non-polymerizable with vinyl chloride and wherein non-polymerizable material is substantially insoluble in water and is miscible with said mercaptan to form a chain transfer composition. The chain transfer composition is added before the start of the polymerization while maintaining colloidal stability.
U.S. Pat. No. 4,471,096 (Sharaby et al, Sep. 11, 1984) relates to a process for the production of vinyl chloride polymers. It has been found that mercapto organic compounds having at least one beta-ether linkage are highly efficient chain-transfer agents in the production of vinyl chloride polymers that do not have the disadvantages of the previously known chain-transfer agents. These chain-transfer agents do not affect the color, odor, and other physical properties of the polymers and do not cause pollution problems.
SUMMARY OF THE INVENTION
This invention is directed to a composition of a chlorinated polyvinyl chloride polymer having improved color that does not utilize polyvinyl alcohol as well as a method for its preparation. A polymer so prepared by this process has utility as pipe and pipe fittings, molding around windows, doors and at baseboards, electrical equipment housings as well as products made by extension sheet blow injection molding and injection molding for home appliances. The composition and method involve polymerizing 100 parts by weight of vinyl chloride optionally with a vinyl component monomer other than vinyl chloride in the presence of from about 0.02 to about 0.5 parts by weight of a surfactant characterized in that the surfactant is a hydroxypropyl methyl cellulose ether having a methoxyl substitution of from 15 percent to 35 percent and a hydroxypropoxyl substitution of from 4 percent to 35 percent to form an intermediate, and (C) chlorinating said intermediate to obtain a chlorinated vinyl chloride polymer.
DESCRIPTION OF THE INVENTION
According to the present invention, chlorinated polymer compositions are provided wherein the polymerization of the monomer or comonomers occurs in the presence of at least one surfactant of hydroxypropyl methyl cellulose ether to yield a product having improved color as well as high Tg.
The hydroxypropyl methyl cellulose ethers used in the process of the present invention are commercially available and are defined primarily by their methoxyl substitution and hydroxypropoxyl substitution. The methoxyl and hydroxypropoxyl substitution are measured and calculated according to ASTM-D 2363. All the percentages of substitution are by weight of the finally substituted material.
The methoxyl substitution of the hydroxypropyl methyl cellulose ethers ranges from 15 percent to 35 percent and preferably from 19 to 25 percent. The hydroxypropoxyl substitution of the hydroxypropyl methyl cellulose ethers ranges from 4 percent to 35 percent and preferably from 4 percent to 12 percent.
The molecular weight of hydroxypropyl methyl cellulose can be expressed as the viscosity of the solution thereof in a solvent therefor. Unless otherwise stated, the molecular weight of hydroxypropyl methyl cellulose is given herein as the viscosity of a 2 weight percent solution of hydroxypropyl methyl cellulose in water as measured using a UBBELOHDE viscosimeter at 20° C.
The viscosity is generally about 5 to about 200,000 mPa's. The hydroxypropyl methyl cellulose ethers which are used as suspending agents for the suspension polymerization of ethylenically unsaturated monomers have preferably a viscosity of from about 5 mPa's, most preferably from about 10 mPa's, to about 400 mPa's, most preferably to about 100 mPa's. The viscosities of 5, 10, 100 and 400 mPa's correspond to number average molecular weights (M
n
) of 10,000, 13,000, 26,000, and 41,000 respectively.
The hydroxypropyl methyl cellulose ethers of the present invention have the above-mentioned methoxyl and hydroxypropoxyl substitution provided that the average molecular weight is less than 50,000. By average molecular weight the number average molecular weight (M
n
) is meant. The preferred average molecular weight is from 5000, most preferably from 10,000, to 40,000, most preferably to 30,000. A particularly preferred range of the molecular weight is from 13,000 to 26,000 which corresponds to a viscosity of 10 mPa's to 100 mPa's. Provided that when the average molecular weight is more than or equal to 50,000, the methyoxyl substitution is more than 24 percent, preferably from 24.5 percent, most preferably from 25 percent, to 35 percent, preferably to 33 percent, and most preferably to 31 percent.
The hydroxypropyl methyl cellulose ethers of the present invention are, for example, useful as suspending agents for the suspension polymerization of vinyl chloride and a vinyl component monomer other than vinyl chloride.
The hydroxypropyl methyl cellulose ethers used for the purpose of the present invention can be produced according to known methods, for example, as described in U.S. Pat. Nos. 2,949,452, and 3,388,082, the teachings of which are included herein by reference. The levels of substitution of the hydroxypropyl methyl cellulose ethers of the present invention can be achieved by increasing the amounts of propylene oxide and methyl chloride and reaction times until the desired substitution level has been reached.
The hydroxypropyl methyl cellulose ethers described herein are used as suspending agents for the suspension polymerization of vinyl chloride and a vinyl component monomer other than vinyl chloride. Preferably, these hydroxypropyl methyl cellulose ethers are used as secondary or co-suspending agents, i.e. together with other suspending agents, for suspension polymerization of vinyl chloride.
The polymerization is done on 100 parts of vinyl chloride or a total of 100 parts of vinyl chloride and vinyl component monomer.
By the term “vinyl component,” it is meant a vinyl type monomer other than vinyl chloride. Such monomers are well known to the art and to the literature and include esters of acrylic acid wherein the ester portion has from 1 to 12 carbon atoms, for example, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, cyanoethyl acrylate, and the like; vinyl acetate; and vinyl aliphatic esters containing from 3 to 18 carbon atoms; esters of methacrylic acid wherein the ester portion has from 1 to 12 carbon atoms, such a
Sharaby Zaev
Vielhaber Robert Gerard
Daulton Julie R.
Dunlap Thoburn T.
Lipman Bernard
PMD Holdings Corporation
Powell Joe A.
LandOfFree
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