DE2408681C2 - Process for the production of moldings - Google Patents

Description

Br

Deformation of the pre-expanded and aged particles in a pressure-resistant, but not gas-tight form, characterized in that the polymerization of styrene is carried out in Presence of 0.001 to 0.5% by weight of one organic brominated compound of the general formula (I) and / or (II):

(D

(Br),

O - R. '"

(Π)

in which R 'and R ", which may be the same or different, each represent a lower, optionally halogen-substituted alkyl radical, preferably a methyl and ethyl radical; R"' and R "". which can be identical or different, represent a completely or partially halogenated hydrocarbon group with 1 to 8 carbon atoms, preferably with bromine, and η has a value of 1 to 5

2. The method according to claim 1, characterized in that the organic brominated compound such a formula:

Br

CH ₂ -CH-CH ₂ -O

! I.

Br Br

O> -O-CH ₂ -CH-CH ₂
Br Br

is used.

3. The method according to claim 1, characterized in that such an organic brominated compound the formula:

CH ₂ -CH-CH ₂
Br Br

is used.

It is known that shaped bodies obtained from foamed styrene-based polymers can be produced are made by being in closed (not gas-tight) forms fine, gaseous or liquid Polymer particles containing blowing agent deformed, at a temperature above the boiling point of the Propellant and the softening point of the polymeric material is worked.

According to a conventional method, the polymer sats containing the blowing agent are first in heated in an open or closed vessel until a predetermined bulk density is reached (Vorversdhäumung) and then after a corresponding- · The aging period is further foamed by heating in a pressure-resistant (non-gas-tight) form (Deformation).

Due to this increase, the particles sinter into a body in the shape of the shape The shaped body is deformed in the form Allow sufficient time to cool to make defoaming to avoid the same after taking it out of the norm.

To reduce the dwell time in the mold has been proposed during the styrene polymer the polymerization of small amounts of organic halogenated compounds and generally bronv,

Incorporate chlorine and chlorobromide derivatives.

However, this method has disadvantages. While, on the one hand, it becomes possible to reduce the dwell time in the mold on the other hand, it becomes difficult to obtain blocks of foamed polymers, which simultaneously show the following properties:

a) short dwell time in the mold;

b) shrinkage of the block thickness <1%;

c) (total) moisture of the foamable particles <03%:

d) homogeneous, fine cell structure of the foamed block; and

e) absence of odors during the pre-expansion stage.

The object of the present invention is therefore to provide one free from the above drawbacks Process for the production of foamable polystyrene

10

15 particles for the production of molded articles with a cell structure and high-quality properties using organic halogenated compounds to reduce the residence time in the mold.

This and other objectives can be achieved by a method for producing moldings on the Foamed polystyrene base comprising the following stages in the order given: Polymerization of StyroL Addition of a blowing agent, preferably during the polymerization, pre-foaming of the foamable particles, aging of the pre-expanded particles and deformation of the pre-expanded and aged particles in a pressure-resistant and non-gas-tight form, which thereby is characterized in that the polymerization of styrene in the presence of 0.001-OA is preferred 0.05-0.2% by weight of an organic brominated compound of the general formulas (I) and / or (II):

R "'- O

O —R "

O —R '

(Br) _n

in which R 'and R "can be the same or different and each represent an optionally halogen-substituted alkyl radical, preferably methyl and ethyl radical; R'" and R "", which can be identical or different, represent a partially or completely - preferably with a bromine-halogenated hydrocarbon group having 1 to 8 carbon atoms, and η is an integer with a value of 1 to 5.

It has surprisingly been found that the foamable polystyrene particles produced according to the invention and the foamed moldings and in particular those produced from these particles Blocks simultaneously have the following properties:

a) short dwell time in the mold, usually equal to or 50% less than that used for Cooling of the pre-expanded particles without organic brominated compound according to the invention manufactured blocks necessary time;

b) shrinkage of the block thickness <1%;

c) (total) moisture of the foamable particles below 0.3%, which is practically identical to those of the organic brominated compounds in the absence of the organic brominated compounds according to the invention manufactured particles;

d) homogeneous fine cell structure of the foamed

35 e)

40

45

55

Blocks; and

complete absence of sharp smells (fumes of bromine, hydrobromic acid or of organic bromine derivatives) during the pre-expansion stage.

The organic brominated compounds to be used in the process according to the invention can be selected from many different products of the above general formulas (I) and / or (II) can be selected.

Particularly good results are achieved with organic brominated compounds of the general formula (I) in which R 'and R ", which can be the same or different, stand for CH3 or CX3 groups, where X is a halogen atom, such as fluorine or bromine or chlorine; R ¹ "and R"", which can be identical or different, represent halogen-substituted alkyl groups of the formula:

-CH ₂ (CHX) _n , -CH ₂ X

are, where m is an integer with a value of 1 to 3 and X is a halogen atom, preferably bromine.

A preferred compound is 2,2-bis- [4- (2,3-dibromopropoxy) -3,5-di-bromophenyl] propane with the formula:

eo

Br

Br

0-CH ₂ -CH-CH ₂

Br

Br-

• Good results can still be achieved with compounds of the general formula (II), in which R '' 'for a halogen-substituted alkyl group of the formula:

--CHi- (CHX) -CH ₂ X

stands in which m is an integer with a value from 1 to 3 and X stands for a halogen atom, preferably bromine. A preferred connection is:

Br

Br

O VO-CH ₂ -CH-CH-,

I I "

Br ^{Br Br}

These brominated compounds are usually styrene prior to its polymerization, optionally in Mixture with the propellant added.

The term "styrene-based polymers" used here includes styrene homopolymers as well as the Copolymers of styrene with other vinyl and / or vinylidene monomers that contain at least 50 % By weight of chemically combined styrene. Such comonomers are e.g. B. a-methylstyrene, im Core halogenated styrenes, acrylonitrile, methacrylonitrile, esters of acrylic and / or methacrylic acid with alcohols with 1 to 8 carbon atoms, as well as N-vinyl compounds such as vinyl carbazole. The copolymers on Styrene-based also include copolymers, in addition to styrene and the above-mentioned vinyl and / or Vinylidene monomers still small amounts of monomers containing double bonds, such as divinylbenzene, contain.

The compounds which can be used as blowing agents for the styrene-based polymers can be selected from many different compounds can be selected, the properties of which are known to those skilled in the art. The aliphatic hydrocarbons, individually or in a corresponding mixture, are particularly suitable Contain 2 to 6 carbon atoms, such as propane, butane, pentane, hexane, cyclohexane, and the halogenated ones Derivatives of aliphatic hydrocarbons with 1 to 3 carbon atoms, such as chlorofluoro derivatives of methane, Ethane and ethylene.

Neber . To the blowing agents, the styrene-based polymers obtainable according to the invention can contain other additives, such as flame extinguishing agents, organic and inorganic fillers, dyes, and antistatic agents. Contain non-agglomeration agents to prevent crumb formation during pre-expansion, plasticizers and other analogous compounds.
The polymerization of styrene, preferably in aqueous suspension, the mixing of the blowing agent, preferably during the polymerization, the pre-foaming of the compressible particles obtained in this way, the aging and conversion of the pre-foamed and aged particles into the molded body by deformation in closed molds are all carried out according to the invention Process that z. B. in "Rigid Plastic Foams" by TN Ferrigno, Reinhold Publishing Corp., New York, USA (1963) are described.

The following examples illustrate the invention.

example 1

With a mixture of the following ingredients, various polymerization tests were carried out in aqueous Suspension carried out:

Parts by weight

100

IJO

Styrene monomer

deionized water
Polymerization initiator

(Mixture of tert-butyl peroxide

and tert-butyl perbenzoate) 0.20

Suspending agent

(89:11 copolymer of acrylic acid
and 2-ethylhexyl acrylate) 0.05

NaCl 0.1

organic brominated compound *) 0.1

*) Different types of bromier were used, in Styrene dissolved compounds with the following formulas:

a) CH ₂ -CH-CH ₂ O

b) Br- <O VO-CH ₂ -CH ^ -CH ₂

0-CH ₂ -CH-CH ₂

Br Br

O VO-CHj-CH = CH ₂

d) Br

0-CH ₂ -CH ₂ -CH ₃

The compounds a) and b) are compounds used according to the invention, while the compounds c) and d) are used for comparison purposes.

The polymerization took place at temperatures between 100 and 140 ° C. for a total of 20 hours. During the polymerization stage, 8 parts by weight of a blowing agent consisting of a mixture of n-pentane and isopentane (weight ratio = 70:30) were mixed into the above suspension. After cooling to room temperature, filtering, washing with water and drying at 35 to 4O ⁰ C for 7 hours, the polymer was sieved mm to obtain foamable polystyrene particles having a diameter from 0.9 to 1.6. These particles contained about 6 weight percent propellant. Yo

The foamable particles were mixed with a common non-agglomerating agent in an amount of 0.15 wt% mixed. Mixing was done in a SAGA screw mixer at room temperature for about 10 minutes.

The thus-treated foamable particles were introduced into a Vorverschäumer (Erlenbach Mod. K2) with Schraubeneinfaß at the bottom and outlet of the prefoamed material at the head in which it by means of steam at 95 to 100 ⁰ C for about 5

Tabel

Minutes were pre-foamed.

The pre-expanded particles were aged in air at room temperature for about 24 hours calmly.

The pre-expanded and aged particles were fed into a RAUSCHER block making press bis introduced for filling a mold of the following dimensions: 1st floor χ 100 χ 50 cm. The deformation took place by means of steam at 1 atm.

The cooling time of the blocks, depending on the type of uses organic brominated compound is the time it takes for a pressure drop within of the block to zero after completion of the steam treatment is necessary.

48 hours after the deformation, the shrinkage and the degree of sintering on the blocks were determined certainly. The sintering was evaluated on a thin plate taken from the central part of the block was cut out by means of a hot wire.

It was determined as the percentage salt of the expanded or foamed particles that broke when the plate was broken. The properties of the foamable Particles and the molded blocks thus obtained are listed in the following table:

From the table above it can be seen that the foamable particles have the same moisture content as the particles produced in the absence of brominated compounds, that odors are completely absent during pre-expansion, that the cooling time compared to blocks of particles produced in the absence of brominated compounds , is noticeably shorter, block shrinkage is <1%, there is a high degree of sintering (70%) and a fine, homogeneous cell structure can be achieved if an organic brominated compound of type a) or b) is used; In contrast, in the other cases, shaped blocks are obtained in which at least one property is not completely satisfactory, such as the cooling time in case d) and the percentage block shrinkage, the degree of sintering, the moisture content of the beads and the odor formation during the pre-foaming in case c ).

Type of organic brominated compound - a b C. d Amount in% - 0.1 0.1 0.1 0.1 (total) moisture of the foamable particles; % 0.22 0.22 0.25 0.75 0.20 Odors during pre-foaming no no no spicy no Properties of the deformed block Density; kg / m * 20th 20th 20th 20th 20th Cool down time; min 60 28 32 23 55 Shrinkage of the block thickness; % <1 <1 <1 3.0 £ 1 Degree of sintering of the broken particles; % 70 70 70 55 70 Cell structure of the foamed beads homogeneous fine homo homo genes genes size size Cells Cells Cells

Claims (1)

Patent claims: 1. A process for the production of moldings based on expanded polystyrene with the the following stages in the order given: polymerisation of the styrene, mixing in a blowing agent, Pre-expansion of the expandable particles, aging of the pre-expanded particles, and