Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-12-07
2004-05-04
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S555000, C524S560000, C524S562000
Reexamination Certificate
active
06730734
ABSTRACT:
The present invention relates to impact modifier compositions which enhance the impact strength performance properties and also lower the viscosity of melt processed plastics resins. In particular, the impact modifier compositions of the present invention improve the impact and viscosity properties of polyvinyl halide resin compounds such as polyvinyl chloride. The invention also provides methods of making these impact modifier compositions.
Plastics resins are used in numerous applications, for example, in plastics sheet, and in blow and extrusion moulded articles such as bottles and containers and building materials. However, articles moulded from resins often suffer from performance problems due to their rigid nature which causes the moulded articles to break or crack easily. To counteract these difficulties it is well known to mix the plastics resins with additive materials, for example, impact strength modifiers to improve the impact strength properties of the moulded articles.
Another important property which markedly influences the efficiency of moulding plastics resins is the viscosity of the resin at the moulding or processing temperature (hereafter ‘melt viscosity’). To ensure that the extrusion and blow moulding pressures are low so as to maximise the efficiency of the extrusion/moulding equipment, it is highly advantageous for the melt viscosity to be kept to a minimum, whilst at the same time ensuring that the shape of the moulded article is retained and that no sagging occurs.
Although impact modifiers improve impact strength, there is a further problem in that they cause the flowability of the resin to decrease, i.e., the melt viscosity of the resin increases. This problem is noted by R. D. Deanin et al in Polym. Material Sci. Eng. 75, 502, 1995. This journal article teaches that the viscosity problem can be overcome by the addition of small amounts, about 5 parts per hundred parts of resin, of solid plasticizers such as dicyclohexyl phthalate. However, although such plasticizers do reduce resin melt viscosity, they do so at the expense of increasing embrittlement or decreasing the impact strength of plastics resins.
There are also several patents which disclose the enhancement of impact strength performance of plastics resins using conventional impact modifiers in combination with various other additives. For example, U.S. Pat. No. 5,780,549 discloses that the impact resistance of PVC compounds is improved by first forming a modified impact modifier by allowing polybutene polymer to absorb into a conventional impact modifier and then adding this modified impact modifier to PVC and processing in the usual manner. U.S. Pat. No. 5,360,853 discloses blending together PVC, an impact modifier and polysiloxane to obtain a PVC resin with enhanced impact strength resistance as compared to PVC resin with the impact modifier alone. Similarly, U.S. Pat. No. 3,428,707 teaches increasing the impact strength of a PVC/impact modifier composition by preparing a blend of PVC and an impact modifier and then milling this blend with polysiloxane. Although these prior art documents disclose that impact strength is improved by the addition of polybutene and polysiloxane, these materials are expensive and this reduces the cost effectiveness of the plastics resin.
Canadian Patent Application No. 2,102,478 discloses that the impact strength of polyvinyl chloride resin may be improved by mixing it with an impact modifier and a lubricant system; the latter comprises a long chain carboxylic acid, a metal salt of a carboxylic acid and mineral oil. However, either the process used to combine the PVC and the other components in the reaction system together, or the choice of reaction components, or both, does not appear to give either a consistently large decrease in the viscosity or a consistently large increase in the impact strength of the melt processed PVC.
A journal article published by D. M. Detweiler et al in Society of Plastics Engineers Annual Technical Conference: Paper V 19, 647, (1973), discloses a study of the interaction of impact modifiers and lubricants. The experiments were conducted by mixing together a polyvinyl chloride resin, an impact modifier, a stabiliser and a lubricant. The results show that the addition of the lubricants can improve the performance of the MBS impact modifier but they apparently have very little effect on the melt viscosity of the PVC resin.
Finally, an article published in Polymer Science U.S.S.R. Vol. 22, No. 10 pp 2395-2402, 1980 by T. B. Zavarova et al teaches that the impact strength of a PVC plastic resin containing a methyl methacrylate/butadiene/styrene (MBS) impact modifier can be increased by the addition of a lubricant such as butyl stearate, glycerin monoricinoleate, transformer oil or &agr;-hydroxyisobutyric acid. However, this prior art teaches, in particular, that the presence of the butyl stearate has no effect on the melt viscosity of PVC-MBS compositions.
The aim of the present invention, therefore, is to provide an impact modifier composition which enhances the impact strength properties of melt processed plastics resins and which also has a lowering effect on the melt viscosity of such plastics resins.
Accordingly, in a first embodiment, the present invention provides an impact modifier composition comprising at least one impact modifier and at least one mineral oil, and further comprising 0-50% by weight of the composition of one or more plastics resins. Preferably the composition comprises 0-20% by weight of the composition of one or more plastics resins.
The invention also provides a method of producing the impact modifier composition described above, comprising mixing together:
a) at least one impact modifier;
b) at least one mineral oil; and
c) 0-50% by weight of the composition of one or more plastics resins.
The at least one impact modifier can be used (i) in latex or emulsion form, in which case the resulting impact modifier composition may be isolated by coagulation or spray drying; or (ii) in dry powder form.
The present invention also provides for the use of the impact modifier composition described above to improve the impact strength and to lower the viscosity of melt processed plastics resins.
Impact modified plastics resins may be prepared by combining one or more plastics resins with the impact modifier composition described above.
A second embodiment of the present invention provides a method of preparing an impact modified plastics resin comprising combining at least one mineral oil with at least one impact modifier and a plastics resin, wherein the at least one mineral oil is not added as, or as part of, an external lubricant for the plastics resin.
Preferably, the amount of impact modifier added to the plastics resin is from 0.1 to 20 parts per hundred parts of resin (PHR).
The invention also provides for the use of the method according to the second embodiment to produce an impact modified plastics resin having a reduced melt viscosity.
The present invention also includes articles that may be made from the impact modified plastics resins described above.
In all of the above embodiments, suitable plastics resins include polyvinyl halide resins, such as polyvinyl chloride; polyalkylene terephthalate polymers; such as polyethylene terephthalate and polybutyleneterephthalate polymers; polycarbonate polymers; polyalkylene terephthalate/polycarbonate polymer blends; acrylonitrile/butadiene/styrene polymers; polyolefin polymers, such as polyethylene, polypropylene; mixed polyolefin polymer blends such as polymer blends of polyethylene and polypropylene polymers; and polyketone polymers. The term “plastics resin” is to be interpreted to include mixtures or blends of one or more of these polymers. The term ‘polymer’ is to be interpreted to include all types of polymer molecules characterized as having repeating units of atoms or molecules linked to each other such as homopolymers co-polymers including block, random, and alternating co-polymers, grafted polymers, and co-polymers terpolymers, etc.
Also, in all of the ab
Chou Chuen-Shyong
Cruz Carlos Alfonso
Hamilton Raymond Gerard
Liwak Susan Marie
Hemenway Carl
Mulcahy Peter D.
Rohm and Haas Company
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