DE938442C - Process for the production of stable solutions of high molecular weight formaldehyde polymers - Google Patents

Description

The Eu-polyoxymethylenes are thermoplastic Polymers can be melted into many valuable objects without the use of solvents be shaped, e.g. B. by spinning, pressing or other deformation. This method has certain drawbacks and limitations, especially when you look at the polyoxymethylene on a light basis wants to apply charring substrate or on complicated shaped bodies. In these cases have solutions significant benefits; but so far no solvent has been found which is not one caused considerable degradation of the polyoxymethylene.

The invention aims at the preparation of solutions of high molecular weight polyoxymethylenes or linear ones Formaldehyde polymers by using phenols and aralkanols as effective solvents. These solutions are conveniently prepared by the formaldehyde polymer with the Stirring solvent at 75 to 16o °.

Such solutions have many advantages. For example, intrinsic viscosity can be measured accurately will; one can cast films and spin fibers from one solution and many others Develop application possibilities that are much more accessible by using solutions are.

The following examples serve only to illustrate the invention without making it exhaustive mark. Unless otherwise stated, parts are parts by weight. The intrinsic viscosity (cf.

LH Cragg in Journ. Colloid Sci., Ι, p. 261 to 269, 1946) was, unless otherwise stated, determined at 60 ° and a concentration of 0.5% ^m p-chlorophenol, which contains 2% a-pinene.

example 1

2 g polyoxymethylene (intrinsic viscosity 1.68) was added to 10.4 g of p-chlorophenol. The mixture was stirred for 5 to 10 minutes while it heated in a boiling water bath. A viscous clear solution was obtained, from which a transparent one tough firm was obtained by spreading the solution on a pad and that Solvent removed at 100 ° under an absolute pressure of ι mm.

Example 2

ι g of a polyoxymethylene (intrinsic viscosity 0.96) was added to 19.6 g of p-chlorophenol. The mixture was heated and stirred for 5 minutes at 85 ^0th After that everything went into solution. The solution was then allowed to cool and the polymer which had precipitated out was filtered off, washed with ether and then dried overnight at room temperature. 0.86 g of polymer were obtained with an intrinsic viscosity of 1.04.

This experiment was repeated, but using a mixture of 19.6 g as the solvent p-chlorophenol and 0.26 g of a-pinene used. The precipitation from this solution corresponded to an 82% strength Recovery of the polymer which had an intrinsic viscosity of 1.07. A reprecipitation out the solvent mixture gave a 94% recovery and caused no significant uptake. 35 Change in the intrinsic viscosity of the polymer. This shows that the polymer in this solvent

! mixture in the preparation of the solution and the Precipitation undergoes essentially no degradation.

There was prepared a solution of 1 g of polyoxymethylene (intrinsic viscosity 0.96) in 19.6 g of benzyl alcohol by heating the mixture with stirring for 5 minutes on 135 ^0th The precipitation corresponded to a 95 ° / _o by weight recovery of the polymer which had an inherent viscosity "of 1.00.

Example 3

It was i a o, 5 ° / ₀ solution of a polyoxymethylene (intrinsic viscosity, prepared in p-chlorophenol / 2 ° / ₀ a-pinene} in m-chlorophenol 68 by stirring the ingredients a short time at 85 °. In m-chlorophenol. The polymer had an intrinsic viscosity of 1.69.

The above experiment was carried out using m-chlorophenol. repeated with 2 ° / ₀ a-pinene as a solvent. The polymer had an intrinsic viscosity of 1.81 in this medium.

Example 4

A specimen of a polyoxymethylene (internal viscosity 1.68) was dissolved in a mixture of m- and p-chlorophenol: dissolved at 80 to 90 ⁰ (1 1). A viscous solution was obtained which gelled on standing overnight at room temperature.

Example 5

In the following table I are given solvents for polyoxymethylene which were tested _{at a concentration of 2 ° / 0.} The solution temperature is that temperature which is necessary in order to dissolve the polymer in a short time, ie in a time of the order of 5 to 10 minutes. The gelation temperature is the temperature at which gelation takes place. It is determined by visual observation of the solution as it cools.

. ' Table I.

solvent

m-chlorophenol

p-chlorophenol

o-chlorophenol

p-tert. Butylcatechin .....

phenol

Trichlorophenol / Phenol 7/10

m-cresol

Resorcinol monomethyl ether
2-bromo-4-tert. butylphenol

α-methylallyl phenol

o- (a-phenylethyl) phenol

2,6-dichlorophenol

o-cyclohexylphenol

α-naphthol

p-tert. Butyl phenol

o-oxybenzyl alcohol

Benzyl alcohol

o-oxyacetophenone

Phenyl-methylcarbinol ...

Methyl p-oxybenzoate

p-oxybenzophenone

Solution temperature

85

85

85

UO

. HO-

100

HO

I25 HO IZO

110

HO 120 HO 120 I30

I25 I30

Gelation temperature

35 50 70 70

75 80

83 85 90

90 90 96

97 96

99 100

HO II4 120 I3O

134 '

The solutions according to the invention give the best results when the polyoxymethylene and the solvent mixture are stirred at temperatures between 75 and 160 °. In the case of special solvent combinations, temperatures below 75 ° can also be used.

The temperature to be used in each case for dissolving depends on the type of solvent used away. If the solvent is normally solid, temperatures must be used at which it will be is liquid. Temperatures above 160 ° are not recommended because this means practically none Advantage achieved.

"To get the polyoxymethylene to dissolve quickly and completely, you need good agitation essential. This is best accomplished in mechanical agitators, Fa-mixers, and the like.

The macromolecular polyoxymethylenes can be used in the preparation of the solutions according to the invention use that have an intrinsic viscosity above 0.6, e.g. B. those produced by block polymerization or by other methods and are described in Table II. ■

Table II

Base material for polyoxymethylene
5 concentration
in p-chlorophenol '
2% pinene Time and temperature
of the solution process Internal viscosity
at 60 ° Ether solution of HCHO with butylamine as
Initiator at -71 °
Spontaneous block polymerization from HCHO
¹⁰ below -8o °
Monomeric HCHO, spontaneously in decahydro-
naphthalene at -50 ° without the addition of any
Initiator or dispersant poly
merized (block polymerization)
¹⁵ Dispersion polymerization of HCHO in deca-
hydronaphthalene, which is polyethylene glycol
Contains dioleate of -30 ° 0.5
0.1
0.2
o, 5 V ₂ hours at 85 ^{0
1 and} ₂ hours at 95 °
1V ₂ hours at 85 ⁰
ι hour at 85 ⁰ 2.31
10.57
^X 5.72
2.11

A suitable method for making polyoxymethylene is to have a cold nitrated solution of anhydrous monomeric formaldehyde in an inert organic solvent introduces into a reaction vessel from which oxygen is purged by an inert gas and that is equipped with a thermometer, stirrer and a charging device for the catalyst. That Reaction vessel is placed in a cold bath, and when the temperature of the reaction mixture between -20 ° and -120 °, the catalyst used in is dissolved in a solvent which is advantageously identical to that solvent in which the formaldehyde is dissolved, added at such a rate that the temperature is within the temperature range selected for the process remains. A more appropriate and preferred one Temperature range is between -30 and -105 °, because then a polymerization can be controlled much more easily than at high temperatures. if the polymerization has ended, which is usually the case in ι to 2 hours, the reaction mixture filtered and the polymer dried, expediently at ordinary temperature.

A typical manufacturing process is as follows: A solution of monomeric formaldehyde was stirred, which by pyrolysis of 100 g of a-polyoxymethylene is obtained, and 800 ecm of dimethyl ether at -101 to -105 ° and continued gradually in the course from 30 minutes to 0.02 mol percent triphenylphosphine, which was dissolved in 40 ecm diethyl ether. After stirring the mass for an additional 70 minutes, the slurry became which precipitated, filtered and the product remaining on the filter twice with 650 ecm of diethyl ether each time washed. The first batch was previously cooled in a cold bath made of dry ice and acetone, and the second approach was at room temperature. The washed product was left in air and then further in vacuo dried. 60 g of snow-white, granular polymeric formaldehyde were obtained.

Another method for producing polyoxymethylene is to dissolve monomeric formaldehyde in a substance which can be a solvent for the monomer but is a nonsolvent for the polymer. The solution is kept at 0 to -120 ° until 1 to 20% of the formaldehyde has polymerized. The precipitating polymer is filtered off, whereupon the polymerization of the formaldehyde in the solution at -20 to -120 ⁰ in the presence of added ionic polymerization catalysts, such as aliphatic amines, which favor the formation of polyoxymethylene, which is separated from the reaction medium and becomes a white granular polymeric product can be dried.

Another method for producing polyoxymethylene is to pass monomeric formaldehyde with stirring in an organic medium which is a nonsolvent for the monomer and the Polymers is. The resulting polymer can be obtained by filtration, centrifugation or others by those skilled in the art known agents are separated from the dispersion medium.

A typical manufacturing process is as follows: Monomeric formaldehyde from the pyrolysis of 69 parts of α-polyoxymethylene is flushed at atmospheric pressure with a slow stream of nitrogen through two traps held at -15 ° and then fed to the top of a reaction chamber set at -30 ^{0 is} held. In this the formaldehyde is taken up as a dispersion in a vigorously stirred mixture of 523 parts of decahydronaphthalene and 5 parts of an oleic acid ester of a polyethylene glycol with a molecular weight of 400. The forming slurry, or the sump is stirred for 30 minutes at -30 ^0, followed by adding the rest of the formaldehyde. The sump is then nitrated to remove the polyoxymethylene that forms. The product is washed with ether, air dried and then vacuum dried. 60 parts (87% of theory) are obtained of snow-white, granular polyoxymethylene which, at a concentration of 0.5 ° / ₀ in p-chlorophenol of 60 °, has an intrinsic viscosity of 1.66.

The inventive method are solutions that are up to 33 or more percent by weight Containing polyoxymethylene, easily produced, with particularly valuable concentration ranges between about 0.1 and 20 percent by weight.

The for the preparation of the solutions according to the Invention used solvents fall into two general classes, namely the phenols and the Aralkanols. These compounds have the common feature of an aromatic nucleus and at least a hydroxyl group which is bound directly or via acyclic carbon atoms to an aromatic C atom can be bonded. Examples of such solvents are phenol, p-tert. Butylphenol,

ίο m-cresol, o-chlorophenol, p-chlorophenol, mixtures of trichlorophenol "with phenol (weight ratio 7: io), ^ -naphthol, methyl p-oxybenzoate, 2-bromo-4-tert. butylphenol, resorcinol monoethyl ether, benzyl alcohol, Tolylmethylcarbinol and the like. The preferred solvents used are the chlorophenols, because they dissolve the polymer at a relatively low temperature.

The solutions according to the invention are very valuable for characterizing the polyoxymethylenes.

High polyoxymethylene solutions can be diluted with either solvents active for the polyoxymethylene or with small amounts of a nonsolvent. By adding large amounts of nonsolvents with stirring, the polyoxymethylene is precipitated in finely divided form. This is a simple and practical method of obtaining the polymer in this Eorm.

The solubility of the polyoxymethylenes generally increases with temperature. When a When warm concentrated solution is cooled below saturation point, slow precipitation occurs or gelation. Such gels are used as coating compounds when a paste is used as a siphon want to apply a solution. However, the properties of a real solution can be improved by heating of the gel can be restored.

The solutions according to the invention can be made by adding pigments, color additives, plasticizers for polyoxymethylene, resins, waxes, antioxidants, corrosion inhibitors, viscosity stabilizers, Acid acceptors such as pinene or phenoxypropylene oxide, metal deactivators, fillers and other valuable substances. ·

The solutions according to the invention are valuable for the manufacture of a variety of articles. Solidification of the polymer can be achieved by evaporating the solvent. Typical Examples of objects that can be made in this way are fibers, threads, films, Tapes, coatings, and plasticized or otherwise modified films. The solutions are also available as Varnishes on wood, metals, glass, paper, textiles, etc., as wire coating compounds or binders for Fiber structures, such as rock wool, glass fibers, and can be used as adhesives.

Films cast from solutions of the polyoxymethylenes are tough and translucent. if Pigments incorporated in the solutions and in these by grinding or other known methods are distributed, the products manufactured in this way are used as printing pastes for the textile industry and the like Purposes.

Filaments can be obtained from the solutions either by dry or wet spinning.

Claims (1)

'Claim: Process for the preparation of stable solutions of high molecular weight formaldehyde polymers, characterized in that macromolecular polyoxymethylene of an intrinsic viscosity of at least 0.6, measured at 60 ° in a _{0.5 ° / 0} igeri solution in p-chlorophenol, which contains 2% a- Contains pinene in one or more aromatic oxy compounds such as phenols and / or aralkanols, e.g. B. chlorophenols and benzyl alcohol dissolves. Cited publications: German Patent No. 310 894; Beilstein's handbook of organ. Chemie, Ί941, 2nd supplement, vol. 1, p. 638. © 509 637 I.S6