Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Specific organic component
Reexamination Certificate
2001-03-13
2002-11-05
Webb, Gregory E. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Specific organic component
C510S188000, C510S451000, C510S395000, C134S008000, C134S022100, C134S022140, C264S039000
Reexamination Certificate
active
06475981
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the use of mixtures of special homopolymers and/or copolymers or graft polymers derived therefrom, chalk and lubricants and/or release agents as freezable compounds in the molding, more particularly by extrusion and injection molding, of compositions containing polyvinyl chloride.
It is known that halogen-containing plastics, more particularly polyvinyl chloride (PVC) or molding compositions produced therefrom, tend to undergo degradation or decomposition reactions when they are exposed to high temperatures. The resulting thermal stressing is problematical above all when it lasts a relatively long time. This is the case, for example, when machines for the molding of mixtures containing polyvinyl chloride are shut down, for example overnight, and then have to be started up again. Such breaks in production are quite common and normal, for example, in the case of extruders or in injection molding. The compositions still present in the machines are exposed to severe thermal stressing for long periods. Since normal processing temperatures for PVC are in the range from about 180 to 200° C. and since, in addition, the cooling of the compositions present in the machine takes place very slowly, the compositions have to be thermally stable for relatively long periods. In addition, they are expected to show certain properties, more particularly a suitable viscosity and adequate freedom from tack, when the machines mentioned are brought back into operation, i.e. started up.
JP-A-05/098072 describes compositions for cleaning machines for molding plastics. These cleaning compositions are prepared by mixing the following three components: (1) thermoplastic resin, (2) neutral salt of alkyl benzenesulfonic acid and (3) basic magnesium stearate.
U.S. Pat. No. 4,838,948 describes a process for cleaning equipment for processing polymers using a composition which contains (1) 92 to 97.4% of a polymer, (2) 2.4 to 6.4% of a mild abrasive and (3) 0.2 to 1.6% of a sulfonated surfactant. Component (1) may be inter alia an acrylic resin while component (2) is selected from the group consisting of calcium carbonate, calcium phosphate, calcium silicate and aluminium silicate.
DD-A-239355 describes a process and a cleaning composition for the rapid and efficient change of pigment in the processing of pigmented thermoplastic molding compositions, more particularly by extrusion and injection moulding. The process is carried out by displacing the pigmented residues from the extruder or the injection molding machine using fiber-reinforced thermoplastic composites. It was found to be of advantage to use a fiber-reinforced thermoplastic composite of polyamide or polyolefins containing up to 75% of chopped glass strands as a special thermoplastic molding composition. Besides these fibrous reinforcing materials, the thermoplastic molding compositions may contain up to 50% of nonfibrous inorganic additives, such as chalk, talcum, kaolin or the like.
DE-C-196 22 579 discloses compositions for cleaning machines for processing plastics, the compositions consisting of the components (1) 95 to 25% of a high molecular weight, non-thermoplastically processable polymethyl methacrylate and (2) 5 to 75% of a thermoplastically processable polymethyl methacrylate. The cleaning composition in question is present in the form of granules or a granular mixture of components (1) and (2) which is passed through the processing machine in the same way as a plastic to be processed therein. By mixing with the cleaning composition, residues of the previously processed resin are discharged from the machine. The cleaning composition is said to be particularly suitable for cleaning injection molding machines and extruders soiled with pigmented or transparent polycarbonates or polymethyl methacrylates.
WO 95/17268 describes abrasive and cleaning compositions containing (1) predominantly one or more abrasive powders, (2) at least one resin and (3) at least one copolymer of an olefin and a (meth)acrylate. In addition, the composition may contain (4) a surfactant. The abrasive (1) may be selected from a number of known compounds, including calcium carbonate. Component (2) is selected from three classes of compounds, namely: polymers of dienes, polymers of resin acids and copolymers of olefins and (meth)acrylates. A typical cleaning composition is described in Example 1: 82% of calcium carbonate, 13% of a polydiene and 5% of an ethylene/methylacrylate copolymer.
DE-A42 02 618 describes a cleaning composition for a resin molding machine containing (1) 50 to 95% of a polyolefin resin with a melt index of 0.01 to 0.5, (2) 0.1 to 15% of an acrylic copolymer, (3) 2 to 30% of a neutral salt of organic sulfonic acid and (4) 0.1 to 10% of basic magnesium carbonate, magnesium hydroxide, potassium carbonate, zinc carbonate or a mixture of two or more components thereof. The composition is said to be suitable for cleaning the molding machine whenever the various types of highly stressed plastics are changed at temperatures of around 400° C.
EP-A-803 338 describes a composition and a process for cleaning machines for processing plastics using a material based on a thermoplastic resin containing a substituted pyrrolidine solvent.
DESCRIPTION OF THE INVENTION
The problem addressed by the present invention was to provide mixtures which would be suitable for use as freezable compounds in the molding of mixtures containing polyvinyl chloride. “Freezable compounds” in the context of the invention are understood to be compositions which, before machines for molding mixtures containing polyvinyl chloride are switched off, are charged with compounds—i.e. the freezable compounds—which remain inside the machines after switch-off and are exposed to thermal stressing therein for long periods.
In particular, the freezable mixtures according to the invention would be distinguished by excellent thermal stability. Above all, they would not show any significant discoloration or increase in viscosity after prolonged thermal stressing. In addition, they would be largely tack-free.
The present invention relates to the use of mixtures containing
a) 20 to 45% by weight of one or more homopolymers and/or copolymers selected from the group of esters of (meth)acrylic acid with monohydric alcohols containing 1 to 4 carbon atoms, ethylene/vinyl acetate copolymers and graft polymers based on the compounds mentioned,
b) 45 to 75% by weight of chalk with particle sizes of 2 to 150 microns and
c) 0.01 to 10% by weight of one or more lubricants and/or release agents with a volatility of less than 0.2% by weight (weight loss after heating in air at 190° C. for 2 hours in an open vessel),
as freezable compounds in the molding of polyvinyl chloride molding compositions. The percentages mentioned for components a) to c) are percentages by weight, based on the mixture as a whole.
One or more homopolymers and/or copolymers is/are used as component a). The homopolymers and/or copolymers in question are homopolymers or copolymers based on esters of acrylic or methacrylic acid with monohydric C
1-4
alcohols as structural elements, ethylene/vinyl acetate copolymers and graft polymers based on the compounds mentioned. Component a) is used in a quantity of 20 to 45% by weight, based on the mixture as a whole. In one preferred embodiment, component a) is used in a quantity of 25 to 40% by weight and more particularly in a quantity of 30 to 35% by weight. In one most particularly preferred embodiment, component a) is selected from polymethyl and polyethyl methacrylates. Basically, the molecular weight of component a) is not critical, although it has been found that compounds with an average molecular weight (number average; Mn) in the range from 800,000 to 4,000,000 are particularly suitable. The range from 800,000 to 2,000,000 is most particularly preferred.
In one embodiment, copolymers based on esters of acrylic or methacrylic acid with methanol and/or ethanol as structural elements are used as component a). In another embodiment, component a) c
Cognis Deutschland GmbH & Co. KG
Drach John E.
Trzaska Steven J.
Webb Gregory E.
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