IE47921B1 - Method of preparing dry mixtures in powder form from polyvinylchloride, lubricating agents and stabilisers,and the manufacture of objects therefrom - Google Patents

Description

The present invention relates to the preparation of polyvinylchloride based dry mixtures in powder form by mixing polyvinylchloride in powder form with one or more lubricating agents and one or more stabilizers.

Methods of preparing dry polyvinylchloride mixtures have been described in numerous publications. In these known methods, and in order to obtain lump-free and well-flowing dry mixtures for the manufacture of blister-free bottles and foils, it was always necessary however to heat to 100 - 130°C and thereafter to cool to 35 - 45°C. These known dry mixtures included glycerol esters of higher fatty acids such as stearic acid and oleic acid as internal lubricants, as well as polyalkene waxes as external lubricants. These however, were exclusively taken up by the polyvinylchloride powder at higher temperatures to obtain a dry, homogeneous, nonadhering and free-running product. (See W.S. Penn, P.V.C. Technology, Applied Science Publishers Ltd., London, third impression pages 265 - 300 especially pate 273 - Dry blending, and page 276 - Mixing of rigid compound, and further pages 315 - 335 - Blow molding P.V.C., and pages 371 - 384 - Compounding and properties of rigid P.V.C.).

Netherlands Patent Specification No. 133.881 refers to the 47831 - 3 use of organic compounds with a long hydrocarbon radical, for example esters of higher fatty acids which have melting points above 40°C as granulating aids or lubricating agents for polyvinylchloride. For these solid lubricating agents to be taken up in polyvinylchloride powder however, heating to above 40°C is necessary.

It has now been found that for the preparation of such dry mixtures, the hitherto necessary heating of the mixtures can if desired, be omitted by the application of special liquid lubricating agents.

According to the present invention therefore there is provided a method for the preparation of polyvinylchloride based dry mixtures of powder form by mixing polyvinylchloride in powder form with one or more lubricating agents and one or more stabilizers, wherein the lubricating agent is isostearic acid, a liquid ester thereof, or a heavy-metal salt thereof (as hereinafter defined).

The expression heavy-metal salt as used herein means a salt of a metal having a specific gravity of greater than 4, as defined in Hackh's Chemical Dictionary, 4th Edition, Ed. J. Grant, McGraw Hill, 1969, page 315, and having lubricating properties.

This invention also provides a method of manufacturing foils, films, bottles, sheet material, sections, pipes and other objects from dry polyvinylchloride mixtures in 7 9 21 - 4 powder form in which that the said dry mixture is a mixture prepared by a method as defined above.

In the method according to the present invention, completely non-adherent and well running dry mixtures can be obtained by mixing (preferably cold mixing) polyvinylchloride in powder form with the said applied liquid lubricating agents and, for example, organic tin-mercaptides as stabilizers, iso-stearic acid and its esters are pre-eminently suitable for this purpose, and when used with known ester-tin10 mercaptides as stabilizers for polyvinylchloride, the favourable action thereof is still considerably enhanced with respect to the slight volatility thereof at higher temperatures. In addition to this, there is an attendant synergistic action, with respect to thermal-stability, and non-adhesion (non-sticking) to metal parts. Furthermore, the synergistic working can be still further increased by cidding small amounts of H^PO^ and dimethyl-sulfoxide during the esterification of the mixture, the dimethylsulfoxide acting as a H^PO^ stabilizer.

Heavy-metal salts of iso-stearic acid have a strong penetrative ability and provide non-adhering and good running dry mixtures by cold mixing. However, they must not be mixed with dialkylthiotin- or with estertin stabilizing agents but exclusively with other heavy-metal salts to inhibit decomposition. 47931 - 5 Preferably, only a minor proportion of the total quantity of the polyvinylchloride (for example 10%) should be mixed with the total quantity of the liquid lubricating agents and the stabilizers, and this by means of a fast mixer with the stirrer thereof rotating at a very high speed, whereafter the rest of the polyvinylchloride (for example 90%) is added and thoroughly mixed with the premix which has already been mixed by the fast mixer. The speed of the latter should preferably be 1400 to 3000 revolutions per minute.

While forming the mixtures according to the present invention no separation thereof occurs through subjecting them to mixing periods of long duration as is the case during the formation of known mixtures with the usual mixers therefore.

Netherlands Patent Application No. 7500991 discloses heavy15 metal salts of fatty acids having a branched hydrocarbon chain with 20-28 carbon atoms as stabilizing agents for polyvinylchloride. These are compounds different from the heavy-metal salts employed according to the present invention. Furthermore, Netherlands Application 7500991 20 makes no mention of the taking up of the concerned heavymetal salts in the polyvinylchloride in powder form in the preparation of dry mixtures in powder form.

The method of preparation accoding to the present invention is illustrated by the following Examples. 478 21 Example 1 Λ fatty acid ester is prepared on the basis of: Iso-Stearic acid Montanic acid 4.224 g (14.9 mol) 239.3 g (0,56 mol) 41.2 g (0,5 mol) Water g (1 mol) Dimethyl-sulfoxide Penta-erythritol 1,4-butandiol Xylene g (0,5 mol) 351.5 g (2.58 mol) 72.4 g (0,8 mol) 300 g (2,8 mol) The mixture is heated under reflux up to 120°C during 25 minutes and in which time it is subjected to a stirring action. Thereafter the water/xylene is distilled off, during which process 15.8 g (0,28 mol) of calcium oxide is slowly added In parts over a period of 25 minutes. The water is separated from the xylene which is then returned to the boiling mass. When no more water is formed, the xylene is distilled in an atmosphere of CO^ and the temperature is allowed to rise to 22O°C. Thereafter cooling takes place down to 120°C and at which temperature the flow CO^ thereto is stopped. Following this, the mixture is supplemented with the following additives: Epoxy-soya oil 464 g (1.56 mol) Tin-mercaptide ester 8.812 g and Di-octyl-tin maleate 2,203 g Thereafter cooling takes place to 30°C This produces a yield of 16.203 g of stabiliser/lubricating agent mixture approximately.

In a combined mixer provided with dosing apparatus and a spray-head, such as prescribed for this process, 100 kg of polyvinylchloride and 2.200 g of the stabiliser/lubricating mixture are cold stirred together and within 3 minutes a completel homogeneous dry mixture is obtained and which is completely dry and non-adherent.

Bottles blow moulded from this mixture are completely transparent, have a high gloss and are odour-free. The production rate for these products is 20% faster than with the usual hot-mixed dry mixtures.

Example 11 3.7 parts (by weight) of a fluid mixture consisting of: Tri-basic lead sulfate 1.5 parts (by weight) Di-basic lead iso-stearate 1.5 parts (by weight) Calcium iso-stearate 0.5 parts (by weight) Iso-stearic acid 0.2 parts (by weight) 3.7 parts (by weight) is cold mixed with 100 parts (by weight) of polyvinylchloride in powder formed and having a K value of 67/68, until a dry powder is obtained.

This powder is suitable for the manufacture of pipes.

Example 111 ,8 parts (by weight) of a fluid mixture consisting of; Tri-basic lead sulfate Di-basic lead iso-stearate Calcium iso-stearate Unsaturated fatty alcohols C18 - C20 Pentra-erythritol iso-tetra stearate 3.5 parts 0.5 parts 0.9 parts 0.4 parts 0.5 parts (by weight) (by weight) (by weight) (by weight) (by weight) .8 parts (by weight) is cold mixed with 100 parts (by weight) of polyvinylchloride in powder form and having a K value of 67/68, until a dry powder is obtained.

The powder obtained is suitable for the manufacture of 15 strongly thermically-resistant sections.

Example IV .8 parts (by weight) of a fluid mixture consisting of: Di-basic lead phosphite Di-basic lead iso-stearate Calcium iso-stearate Unsaturated fatty alcohols parts (by weight) 1.5 parts (by weight) 0.5 parts (by weight) C18 - C20 0.4 parts (by weight) Pentra-erythritol iso-tetr.i stearate 0.4 parts (by weight) .8 parts (by weight) is cold mixed with 8,0 parts Omya BSH (chalk), 2.0 parts 5 titanium-dioxide and 100 parts (by weight) of polyvinylchloride, in powder form and having a K value of 67/68, until a dry mixed powder is obtained.

This powder is suitable for the manufacture of blinds.

Claims (7)

1. A method for the preparation of polyvinylchloride based dry mixtures in powder form by mixing polyvinylchloride in powder form with one or more lubricating agents and one or 5 more stabilizers, wherein the lubricating agent is isostearic acid, a liquid ester thereof or a heavy-metal salt thereof (as hereinbefore defined).

2. A method as claimed in Claim 1 wherein the mixing is cold mixing. 10

3. A method as claimed in Claim 1 or 2, in which initially only a minor proportion of the total polyvinylchloride is mixed with the total quantity of lubricating agent and stabilizer, the resulting mixture is homogeneously mixed with the rest of the polyvinylchloride. 15

4. A method as claimed in Claim 1 and substantially as hereinbefore described with reference to any of the Examples.

5. A dry mixture when prepared by a method as claimed in any of Claims 1 to 4,

6. A method of manufacturing foils, films, bottles, 20 sheet material, sections, pipes and other objects from dry 4 7 9 21 - 11 polyvinylchloride mixtures in powder form, in which the said dry mixture is a mixture as claimed in claim 5.

7. A product manufactured by a method as claimed in Claim