Phosphite Stabilized Polyvinyl Chloride Containing Resins

This invention relates to the stabilization of halogen-containing resins, particularly a polyvinyl chloride.

When a halogen-containing resin is processed, it will be exposed to a high temperature and therefore there will occur decomposition, dehydrochlorination and discoloration. It is already known that various stabilizers and stabilizing assistants are added to prevent such deterioration, as is described, for example, in British Patent No. 1,180,398.

It is also known to use these stabilizers and stabilizing assistants together to develop synergistic effects. Among such known stabilizing assistants are antioxidants, polyhydric alcohols and organic phosphites. However, these known stabilizers and stabilizing assistants are not fully satisfactory and are required to be improved. Further, the requirement for nontoxication is strong recently. In the case of nontoxic mixing without the use of Cd of Pb, there is no particularly satisfactory stabilizer today.

As a result of making hard investigations in view of these points, the present inventors have reached the present invention by finding that certain organic phosphites are very effective to this object.

Thus, the present invention is to provide a process for stabilizing a halogen-containing resin, which comprises incorporating from 0.01 to 10 parts by weight per 100 parts by weight of the said resin of a phosphite having the formula (I), ##EQU2## wherein one or two of groups, R.sub.1, R.sub.2 or R.sub.3 has the formula, R(OC.sub.n H.sub.2n).sub.m --, in which R is an alkyl unsubstituted or substituted with at least one hydroxyl or chlorine, an alkenyl unsubstituted or substituted with at least one hydroxyl or chlorine, or an aralkyl, n has a value of from 1 to 4, and m has a value of from 1 to 8, and the remaining group R.sub.1, R.sub.2 and/or R.sub.3 is an alkyl unsubstituted or substituted with at least one hydroxyl or chlorine, an alkenyl unsubstituted or substituted with at least one hydroxyl or chlorine, an aralkyl or an unsubstituted aryl.

The phosphite of the present invention can be prepared by reacting a phosphite of the formula (II),

wherein R.sub.4 is an aryl or the same as R, with an alcohol of the formula (III),

wherein R, m and n are as defined above, in the presence of a basic catalyst.

In the present specification, the term "alkyl" is intended to mean an alkyl having 1 to 18 carbon atoms, the "aryl" is, for example, phenyl, tolyl, xylyl, tert.butylphenyl, octylphenyl, nonylphenyl, chlorophenyl, hydroxyphenyl, etc., the "aralkyl" is, for example, benzyl, phenethyl, etc. and the "alkenyl" is to mean an alkenyl having 2 to 24 carbon atoms, for example, oleyl, ricinoleyl, etc.

Examples of the alcohol are n-butoxyethanol, n-butoxydiethyleneoxyethanol, 2-ethylhexyloxypropanol, nonyl-phenoxypropanol, lauryloxyethanol, oleyloxyethanol, ricinoleyloxyethanol, 2-benzyloxyethanol, butoxyethoxyethanol, etc.

The basic catalyst includes sodium hydroxide, potassium hydroxide, calcium hydroxide and lithium hydroxide.

In the present invention, favorable phosphites are represented by the formula, ##EQU3## wherein R and n are as defined above. The most favorable ones are 2-(2-butoxyethoxy)ethyl diphenyl phosphite which is a novel compound, 4-methoxybutyldiphenyl phosphite, 3-(2-ethylhexyloxy)propyldiphenyl phosphite, 2-benzyloxyethyldiphenyl phosphite and 2-isopropylbenzyloxyethyldiphenyl phosphite.

The reaction between triphenyl phosphite and said alcohol is conducted in the presence of said basic catalyst at a temperature of 80.degree. to 180.degree.C. The alcohol (R.sub.4 OH) by-produced may be removed during the reaction of after the completion of the reaction under a reduced pressure. The completion of the reaction can be confirmed by an amount of said phenol removed, and the reaction is usually conducted for 1 to 10 hours. Several typical examples of these phosphites and their refractive indexes at 25.degree.C. and forms are shown in the following table.

However, the phosphites (I) of the present invention are not limited to these specific ones indicated in this table.

The phosphites (I) of the present invention can be used together with any other generally known stabilizers, stabilizing assistants, antioxidants and ultraviolet ray absorbents.

Examples of these known stabilizers are carboxylates, mercaptides and mercaptates of Cd, Ba, Zn, Ca, Pb, Sn and R.sub.2 Sn (R: alkyl).

Particularly, in the case of a nontoxic mixture used together with aliphatic acid salts of Ca--Zn, there will be given heat-resistance, transparency and coloring prevention much higher than in the case of using a known organic phosphite together with said salts. Further, in the case of using the stabilizer of this invention together with a Cd--Ba type stabilizer, particularly the weather-proofness of the resin will be greatly improved.

Examples of stabilizing assistants are epoxy compounds, other known organic phosphites and polyhydric alcohols.

Further, the phosphite (I) of the present invention serves also as a dropless agent which has the ability to prevent the formation of a water drop and drop flowing agent and also an antistatic agent. Particularly, even if this organic phosphite is used alone, it will be effective but, if it is used together with any other dropless agent or antistatic agent, it will develop a synergistically greater effect.

The organic phosphite of the present invention can also be used together with such additives for halogen-containing resins as, for example, a lubricant, filler and plasticizer.

The halogen-containing resin to be stabilized by the present invention may be polyvinyl chloride, a polymer blend of a polyvinyl chloride with any other blendable resin or a copolymer with vinyl chloride. The amount of the organic phosphite of the present invention to be added to a resin is 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight per 100 parts by weight of the halogen-containing resin.

The present invention will be explained in more detail with reference to examples, which are only illustrative but not limitative. Parts are by weight.

248.2 g. (0.8 mol) of triphenyl phosphite and 131.2 g (0.81 mol) of 2-butoxyethoxyethanol were put into a flask of 500 ml. and 0.1 g. of sodium hydroxide was added thereto to react at 140.degree.C. for 4 hours. The liberated phenol was distilled away by distillation under a reduced pressure (at 60.degree.C. under 5 mm.Hg). Then the residual solution was filtered to obtain colorless transparent 2-(2-butoxyethoxy)ethyl diphenyl phosphite (Compound 9) as a filtrate.

Refractory index: 1.5110 (at 25.degree.C.)

Specific gravity: 1.1910 (at 25.degree.C.)

Other phosphites can be also produced in the same manner.

100 parts of a polyvinyl chloride resin (SX-11 produced by Sumitomo Chemical Company, Limited), 50 parts of dioctyl phthalate, 0.5 part of cadmium stearate, 0.5 part of barium stearate and 0.5 part of each of organic phosphites shown in Table 2 were mixed together and the mixture was kneaded on two rolls at 165.degree.C. for 10 minutes to make a sheet. The thermostability of this sheet in a gear type deterioration tester, the press-test result (transparency and coloration) and weather resistance to the nature are shown in Table 2.

100 parts of a polyvinyl chloride resin (SX-11 produced by Sumitomo Chemical Company, Limited), 50 parts of dioctyl phthalate, 0.4 part of zinc stearate, 0.6 part of calcium stearate, 3 parts of epoxyated soybean oil and 1.0 part of each of organic phosphites in Table 3 were mixed together and the mixture was kneaded on two rolls at 165.degree.C. for 10 minutes to make a sheet.

The thermostability of this sheet in a gear type deterioration tester and the results of press test (transparency and coloration) are shown in Table 3.

100 parts of a polyvinyl chloride resin (SX-11 produced by Sumitomo Chemical Company, Limited), 50 parts of dioctyl phthalate, 1.5 parts of KV-39A-5 (produced by Kyodo Chemical Company Ltd.) as a stabilizer, 0.4 part of cadmium stearate, 0.2 part of barium stearate, 1.0 part of each of organic phosphites in Table 4, further 0.5 part of sorbitan distearate as a drop flowing agent and 0.5 part of sorbitan monopalmitate were mixed together and the mixture was kneaded on two rolls at 170.degree.C. for 10 minutes to make a sheet.

The thermostability of this sheet in a gear type deterioration tester, the results of mealing test and the droplessness are shown in Table 4.

100 parts of a polyvinyl chloride resin (SX-7G produced by Sumitomo Chemical Company, Limited), 10 parts of MBS (Kaneace B-12 produced by Kanegafuchi Chemical Co.), 4 parts of epoxidized soybean oil, 0.5 part of stearic acid, 1.0 part of a stabilizer KH-300A-6 (produced by Kyodo Chemical Company, Ltd.), 0.3 part of calcium stearate as a stabilizer, 0.3 part of zinc stearate and 0.5 part of each of organic phosphites in Table 5 where mixed together and the mixture was kneaded on two rolls at 180.degree.C. for 5 minutes to make a sheet.

The results of mealing test of this sheet at 185.degree.C. and the results of press test are shown in Table 5.

2.0 parts of each of organic phosphites in Table 6 were added to a paste sol consisting of 100 parts of a polyvinyl chloride resin (Sumilit PXNH produced by Sumitomo Chemical Company, Limited) and 60 parts of dioctyl phthalate and the heat-resistance and sol viscosity variation of the mixture were tested. The results are shown in Table 6.

As clear from this table, the phosphite of the present invention is very effective not only to the heat-resistance (discoloration prevention) but also to the prevention of the variation of the viscosity of the sol.