Claims
- 1. A process for the manufacture of a modified polyolefin comprising the steps of:
- (a) admixing molten polyolefin with 20-2000 ppm of sulphur trioxide/trimethylamine complex at a temperature above 210.degree. C., said polyolefin being a homopolymer or copolymer of alpha-olefins selected from alpha-olefins having 2-10 carbon atoms, and mixtures thereof, said alpha-olefin being a non-aromatic hydrocarbon, and
- (b) forming the modified polyolefin so obtained into a shaped article;
- wherein molten polyolefin is admixed with a concentrate composition comprising a second polyolefin and said complex at a temperature below 210.degree. C. prior to the admixing at a temperature above 210.degree. C., said composition having been formed by admixing the second polyolefin in molten form with the complex at a temperature below 210.degree. C., said second polyolefin having a shear viscosity that is not more than 50% of that of the polyolefin at 200.degree. C. and a shear rate of 400 sec.sup.-1.
- 2. The process of claim 1 in which the concentrate composition contains 200-40 000 ppm of the complex.
Priority Claims (1)
| Number |
Date |
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| 485652 |
Jun 1985 |
CAX |
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BACKGROUND OF THE INVENTION
This is a division of application Ser. No. 756,225, filed July 18, 1985.
The present invention relates to modified polyolefins and especially to polyolefins that have been modified by treatment with sulphur trioxide/trimethylamine complex.
Polymers of ethylene and/or other hydrocarbon alpha-olefins, espcially homopolymers of ethylene or propylene and copolymers of ethylene with C.sub.3 -C.sub.10 alpha olefins, may be fabricated into a wide variety of articles, including film, fibres, sheet, moulded articles and/or pipe. If such articles are desired in a colour other than the natural colour of the polymer, it is often possible to pigment the polymer or, especially if the polymer surface has been suitably treated, to print the fabricated article.
The use of pigments and/or printing techniques depends on the nature of the fabricated article and the process used in the manufacture of the article. For example, if it is desired to produce a coloured polyolefin film, small amounts of pigment may be incorporated into the polymer composition prior to or during extrusion of the composition into film. However, coloured films produced in this manner are normally much less transparent than films produced from compositions that do not contain pigments. If the natural transparency of the polymer is to be retained, other means e.g. dyeing, must be used to colour the polymer composition.
Although it is known that polyolefins are dyeable by a small number of dyes, polyolefins are generally characterized as not being receptive to dyes in the absence of modification of the polymer to render it receptive to dyes. Techniques for such modification are known. For instance, a suitable comonomer may be copolymerized into the polyolefin during the manufacture of the polymer but such comonomers tend to be catalyst poisons and cannot be fed into some polymerization processes.
Alternatively, polyolefins may be treated, in the presence of free-radical catalysts, to incorporate carboxyl, anhydride, hydroxyl and other potentially dye receptive sites into the polymer. However, processes for such treatment tend to be expensive, especially if unreacted monomers must be removed from the polymer and/or if complex apparatus is required. Dye receptive groups may also be introduced into polyolefins by blending the polyolefin with a polymer which is itself dyeable. The resultant blends may, however, be more expensive and/or have significantly different physical properties from those of the polyolefin per se.
A modified polyolefin, especially a polyolefin capable of being dyed with basic dyes, and a process for the manufacture of such a modified polyolefin in conventional equipment and in the absence of free-radical catalysts has now been found.
Accordingly, the present invention provides a modified polyolefin formed by the reaction of molten polyolefin with sulphur trioxide/trimethylamine complex, said polyolefin being a homopolymer or copolymer of alpha-olefins selected from the group consisting of alpha-olefin having 2-10 carbon atoms, or mixtures thereof, said alpha-olefin being a hydrocarbon.
In a preferred embodiment of the modified polyolefin of the present invention, the polyolefin is a homopolymer of ethylene or propylene, or a copolymer of ethylene and at least one C.sub.3 -C.sub.10 alpha-olefin.
The present invention also provides a process for the manufacture of a modified polyolefin comprising the steps of:
(a) admixing molten polyolefin with 20-2000 ppm of sulphur trioxide/trimethylamine complex at a temperature above 210.degree. C., said polyolefin being a homopolymer or copolymer of alpha-olefins selected from alpha-olefins having 2-10 carbon atoms, or mixtures thereof, said alpha-olefin being hydrocarbon, and
(b) forming the modified polyolefin so obtained into a shaped article.
In a preferred embodiment of the process of the present invention, the polyolefin is a homopolymer of ethylene or propylene, or a copolymer of ethylene and at least one C.sub.3 -C.sub.10 alpha-olefin.
In a further embodiment, the temperature of the molten polyolefin is above the melting point of the complex.
In another embodiment, the temperature of the molten polyolefin is 239-280.degree. C.
In the present invention, the polyolefins may be homopolymers of alpha-olefins having 2-10 carbon atoms, especially homopolymers of ethylene and of propylene. Alternatively, the polyolefins may be copolymers of alphaolefins having 2-10 carbon atoms, especially copolymers of ethylene with propylene, butene-1, hexene-1, 4-methylpentene-1 and/or octene-1. The polyolefins may be blends and/or admixtures of such homopolymers and copolymers. Techniques for the manufacture of these polyolefins are known in the art. In the present invention, the alphaolefins are hydrocarbons.
The polyolefins are normally solid polymers of the type known to be formed into articles by using extrusion, injection moulding and other forming techniques. For example, if the polymers are of the type frequently referred to in the trade as polyethylene viz. homopolymers of ethylene and copolymers of ethylene with C.sub.4 -C.sub.10 alphaolefins, such polymers will have densities of at least about 0.890 g/cm.sup.3, especially 0.915-0.970 g/cm.sup.3, and melt indices (as measured by the procedure of ASTM D-1238 (Condition E)) of less than about 200 dg/min and especially less than about 150 dg/min. The melt index, in particular, will depend on the intended end-use of the polyolefin. For example, polyolefins intended for fabrication into film usually have a melt index of less than 10 whereas those intended for fabrication into articles by injection moulding techniques will usually have higher values of melt index. The present invention will generally be described herein with reference to polyethylene as the polyolefin.
The complex of sulphur trioxide and trimethylamine is known in the art. For example, the production of sulphur trioxide/trimethylamine complex is described in U.S. Pat. 3 334 139 of J. Rosin, issued Aug. 01, 1967.
The modified polyolefins of the present invention are formed by the reaction of the polyolefin with the sulphur trioxide/trimethylamine complex. A particularly preferred method involves reaction of the complex with molten polyolefin, as is described in further detail hereinafter.
It is preferred that the modified polyolefin be prepared by reaction with 20-2000 ppm of the complex. Even such low levels as 20 ppm of the complex result in a modified polyolefin that is dyeable, although the extent of dyeing that is possible, especially at short processing times, may not be acceptable for some end-uses. High levels of the complex may be incorporated into the polyolefin, but difficulties may be experienced in the preparation of the modified polyolefin. For example, with high levels of the complex, the resultant modified polyolefin may exhibit a dark hue and/or excess trimethylamine may remain in the modified polyolefin even after contact with a dye bath.
The modified polyolefin may be used in a variety of end-uses, it being understood that the preferred amount of the sulphur trioxide/trimethylamine complex in the modified polyolefin will likely be dependent on the intended end-use. For example, the modified polyolefins may be used as dyeable polymers, to promote adhesion to the polyolefin, to facilitate retention of additives in the polyolefin and the like.
In the preferred process for the manufacture of the modified polyolefin, molten polyolefin is admixed with 20-2000 ppm of the complex of sulphur trioxide and trimethylamine. The admixing is carried out at a temperature of above 210.degree. C., especially above the melting point of the complex, and particularly at temperatures of less than about 45.degree. C. above the melting point of the complex. It is preferred that the complex be admixed with the polyolefin at a temperature in the range of 239-280.degree. C.
Even though it is stated herein that the polyolefin and complex be admixed at a temperature above 210.degree. C., the complex and polyolefin should be first admixed, preferably uniformly admixed, at tempertures below 210.degree. C. so as to obtain a uniform admixture of polyolefin and complex prior to any significant reaction therebetween. It is believed that high localized concentrations of the complex, as could occur in the event of poor mixing, may be detrimental in that minute dark particles may be formed which may be noticeable in thick sections of the modified polyolefin.
As is exemplified hereinafter, a preferred method of dispersing the complex in the polyolefin is to coat the complex onto particles of a compatible polyolefin that has a lower shear viscosity under melt processing conditions than does the polyolefin being modified, as is disclosed in the patent application of G. White filed concurrently herewith. The thus coated particles are admixed in suitable proportions, but as a concentrate, into the polyolefin being modified. Alternatively, the complex may be blended into the lower viscosity polymer at temperatures below 210.degree. C., to form a blend (concentrate) that is then admixed with the polyolefin being modified. In such concentrates, it is preferred that the concentrate contain 200-40 000 ppm of the complex and that the polymer of the concentrate have a shear viscosity that is not more than 50% of that of the polymer of the intended composition, when measured at 200.degree. C. and at a shear rate of 400 sec.sup.-1.
A physical admixture of polyolefin and complex, in a suitable form, may be prepared prior to the feeding of the admixture to an extruder or the like; the suitable form may for example be coated polymer or a blend as discussed above. The polyolefin and complex are preferably of a similar particle size to facilitate uniform mixing, in the event that the complex is not coated on particles of the polymer.
In the admixing of the polymer and complex, it is preferred that a low temperature be used, provided that such temperature is above the melting point of the complex, to reduce the extent of any side reactions involving the complex and/or modified polyolefin.
The molten modified polyolefin thus obtained is formed into a shaped article. Such articles may be pellets or other comminuted forms of the modified polyolefin. However, it is preferred that the modified polyolefin be formed directly into film, moulded articles or the like.
The modified polyolefin may be admixed with stabilizers and other additives known for use in polyolefins, pigments, fillers and the like or subjected to dyeing processes. In dyeing processes, it is preferred that the dye bath does not contain so-called levellers e.g. sodium sulphate.
US Referenced Citations (3)
Divisions (1)
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| Parent |
756225 |
Jul 1985 |
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Patent Grant
4801656
