DE2826459A1 - EXPANDABLE POLYSTYRENE PARTICLES AND METHOD OF MANUFACTURING THEREOF - Google Patents

Description

. Dfpl.-lng. P. WIRTH Dr. V. SCHMfED-KOWARZfK
German-lng. G. DANNENBERG Dr. P. WEINHOLD - Dr. D. GUDEL

335024 SIEGFRtEDSTRASSE

TELEPHONE: C089) _{8 () 00 MONKS} 4Q

Case: MN 2444 and MN 2445

Montedison SpA Foro Buonaparte 31 Milan / Italy

Expandable polystyrene particles and processes for their manufacture.

809881/0927

The present invention relates to foamable polystyrene particles with improved properties, particularly on foamable polystyrene particles used in the manufacture of Molded parts, in particular large blocks, are suitable, which have a uniform cell structure and a particularly require a short dwell time in the mold, as well as a process for the production of these particles.

It is known that molded parts can be produced from foamed styrene polymers by adding polymer particles that are gaseous or contain liquid propellants, are compression molded in closed, but not gas-tight molds, with one Temperature above the boiling point of the blowing agent and the softening point of the polymer is used.

The usual procedure is that the polymer particles containing the blowing agent, first in an open or closed vessel heated (pre-foamed) until a previously determined bulk density is reached, after which - after a suitable aging time - the aged particles be further foamed by heating (compression molding) in a pressure-resistant, but not gas-tight form. By this heating it is achieved that the particles stick together to form a body which has the shape of the mold.

After compression molding, the molded part is allowed to cool in the mold for a sufficient time to prevent the part from deforming when it is removed to avoid out of shape.

In order to shorten the residence time in the mold, it has been proposed to add small amounts of halogen-containing to the styrofoam to add organic compounds.

809881/0927

However, the known compounds suitable for this purpose have several disadvantages in practice; they develop bad odors during pre-foaming or they prevent that at the same time other desirable properties are obtained, such as:

- shrinkage of the block thickness of not more than 1 %;

- Moisture content of the foamable particles of not more than 0.3% i and

- fine-cell, homogeneous structure of the foamed block.

An object of the present invention to provide of expandable polystyrene particles that are suitable for the production of molded parts with a fine-cell, homogeneous structure having the above shrinkage and moisture properties and only require a very short residence time in the mold.

It has now been found that this object can be achieved by using schäurabare polystyrene particles which in addition to the propellants, in an amount not more than about 1% by weight at least one compound of the general formula (I) or (II):

A-R,

(D

A-R,

(ID

809881/0927

where A = -0- or -COO- can mean and if A = -0- is:

R ₂ and R ^, which can be the same or different, optionally halogen-substituted alkyl, cycloalkyl and / or phenyl groups;

Ri- a non-halogen-substituted alkyl group with about 4-30 carbon atoms or a wholly or partially halogen-substituted alkyl group with about 9-30 carbon atoms; X is a halogen or an optionally halogen-substituted alkyl group having 1 to about 8 carbon atoms; m is an integer from 0 to about 4;
η is an integer from 0 to about 5; and

R. and R ^, which may be the same or different, optionally Halogen-substituted alkyl groups with 1 to about 30 carbon atoms, but when Rp and R, Are alkyl groups, X = bromine and m = 2, R ^ and R ^ are not Halogen-substituted alkyl groups having 1 to about 30 carbon atoms or completely or partially halogen-substituted Mean alkyl groups of about 9-30 carbon atoms;

and, if A = -COO-:

.R ₁ , R ^ and Rc, which can be the same or different, optionally halogen-substituted alkyl groups having 1 to about 30 carbon atoms;

Rp and R ,, which can be the same or different, optionally Halogen-substituted alkyl, cycloalkyl or phenyl groups;

X is a halogen or an alkyl group having 1 to about 8 carbon atoms;

m = an integer from 0 to about 4 and η = an integer from 0 to about 5,

contain.

The foamable polystyrene particles of the present invention can be obtained by adding styrene in the presence of at least one compound of the above general formula (I) or (II) polymerized as well as a conventional blowing agent.

809881/0927

In order to produce the foamed moldings, the inventive foamable particles first pre-expanded, then aged and then in a pressure-resistant, however not gas-tight form molded.

The foamable polystyrene particles according to the invention and the foamed moldings produced therefrom, in particular Blocks, have the following properties at the same time:

a) short dwell time in the mold, generally less than 50 / ö of the time it takes for blocks to cool, which from foamed particles which are not the above mentioned compounds of the general formula (i) or (II) contain, have been produced;

b) Shrinkage of the block thickness by less than 1 % \

c) (Total) moisture of the foamable particles = less than 0.3 % i practically the same moisture content as in the case of particles which have been prepared in the absence of the organic compounds of the general formula (I) or (II);

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

e) complete absence of pungent odors during pre-expansion.

The compounds which are incorporated into the expandable polystyrene particles according to the invention can be selected from a variety from products corresponding to the above formula (I) or (II).

It has been found that, of these compounds, those which do not contain halogen and in which R ₁ , R 4 and R _{5 have} more than 8 carbon atoms are of particular interest for use on an industrial scale.

809881/0927

The compound (s) of the general formula (I) and / or (II) are usually the styrene or the monomeric mixture before or during the polymerization, optionally in a mixture with the propellants added.

It is true that even very small amounts of the abovementioned compounds, such as about 0.005 % by weight, based on the monomer, can influence the polymer properties; in practice, however, the best results are achieved with amounts of about 0.05-0.2 wt.

In the present specification and claims, the term "styrene polymer" refers to styrene homopolymers as well as copolymers of styrene and other vinyl and / or vinylidene monomers, the copolymers at least about 50% by weight of chemically bound styrene.

Examples of such comonomers are cd-methylstyrene, am Core halogenated styrenes, acrylonitrile, methacrylonitrile, esters of acrylic and / or methacrylic acids with alcohols, the Containing 1 to 8 carbon atoms, N-vinyl compounds, such as Vinyl carbazole, etc. The class of the mixed styrene polymers also includes mixed polymers which, in addition to styrene and optionally the just mentioned vinyl and / or vinylidene monomers still small amounts of monomers with two double bonds, such as Divinylbenzene.

In addition to the compounds of the general formulas (I) and (II), in the polymerization process according to the invention generally known propellants are added.

Aliphatic hydrocarbons are particularly suitable as blowing agents, either alone or in suitable mixtures, with about 2-6 carbon atoms, such as propane, butane, n-pentane, Isopentane, hexane, cyclohexane and the like, as well as halogen-containing Derivatives of aliphatic hydrocarbons having 1 to about 3 'carbon atoms, such as chlorofluoro derivatives of Methane, ethane and ethylene.

809881/0927

In addition to the driving agents, the styrene polymers according to the invention can other additives, such as flame extinguishers, organic and inorganic fillers, dyes, antistatic agents, anti-agglomeration agents for prevention the formation of lumps during pre-expansion, plasticizers and other similar compounds.

The polymerisation of styrene, preferably in an aqueous suspension, the addition of the blowing agent, the pre-foaming of the foamable particles, aging and manufacturing of molded parts from the pre-expanded and aged particles by compression molding in closed molds is made according to known methods carried out, which have been described in detail, for example in "Rigid Plastic Foams" by T.N. Ferrigno, Reinhold Publishing Corp., New York, USA (1963).

The following examples serve to explain the present invention in more detail.

Examples 1-13

Various polymerization tests were carried out with aqueous suspensions of mixtures of the following components:

- styrene monomer 100 wt -.%

- deionized water 100 ^H

- Polymerization initiator (mixture of tert-butyl peroxide and

tert-butyl perbenzoate) 0.2% by weight

- Acrylic acid / 2-ethylhexyl acrylate copolymer (Weight ratio =

89:11) as suspending agent 0.05% by weight 6

- NaCl 0.10 "

- Compound of general formula (I) or (II) of the type and in the amount indicated in the table.

809881/0927

The polymerization was carried out at temperatures between 100 and 140 ° C carried out for a total of 20 hours.

During the polymerization, 8 parts by weight of a Trcihrrittels, which consisted of a mixture of n-pentane and isopentane, were added to the suspension mentioned. After cooling to room temperature, filtering, washing with water and drying for 7 hours at 35-4O ⁰ C, the polymer was sieved to obtain foamable polystyrene particles with a diameter between 0.9 and 1.6 mm. These particles contained approximately 6% by weight of propellant.

The foamable particles were made up of about 0.15% by weight of a conventional anti-caking agents mixed.

Mixing was done in a screw mixer "SAGA" at room temperature carried out for a period of about 10 minutes.

The foamable particles treated in this way were placed in a pre-expander (Erlenbach Mod. K2), which was equipped with a screw inlet at the lower end and with an outlet for the pre-expanded material at the upper end, in which it was at 95 with the aid of steam - 100 ⁰ C were pre-foamed for about 5 minutes.

The pre-expanded particles were then allowed to age in air at room temperature for about 24 hours.

The pre-expanded and aged particles were placed in a Rauscher block press until the shape, which had the dimensions: 100 χ 100 χ 50 cm was completely filled. The compression molding was carried out with the aid of steam under a pressure of 1 atm carried out. Then, the molded block, the density, cooling time, shrinkage, thickness and degree of Sintering determined. These values are listed in the table below.

809881/0927

"Cool down time" of the blocks means the time required for the pressure within the block to decrease to zero after the steam treatment has ended.

The shrinkage as well as the degree of sintering of the blocks were determined 48 hours after compression molding.

The degree of sintering was obtained from a thin plate obtained by hot slaughtering from the central part of the block was determined, expressed as a percentage of the foamed particles that cracked when the plate was broken became.

The cell structure of the foamed particles was the same for all samples homogeneous and fine-celled.

809881/0927

Tabel

ο co co

Example no. 1 - 2 a 3 b 4th C. 5 d 6th e 7th Type of connection of general
Formula (I) or (II) 0.20 0.1 0.1 0.1 0.05 0.05 f Amount, % no 0.28 0.28 0.26 0.26 0.28 0.1 Total moisture content of the
foamable particles, % no no no no no 0.26 Odors during pre-expansion 20th no Properties of the compression molded
Blocks 62 20th 20th 20th 20th 20th Density, kg / cnr 70 28 29 20th 24 22nd 20th Cool down time, minutes <Λ 70 70 70 70 70 24 Degree of sintering, % <1 <Λ <1 <1 <1 70 Shrinking block thickness, 96 4.1

- 13 -

Tabel

co ο co

Example no.

Type of compound of the general formula (I) or (II), amount, % total moisture content of the expandable particles, % odors during the pre-expansion

Properties of the compression molded block

Density, kg / cnr cooling time, minutes degree of caking,% shrinkage of the block thickness,%

8th G 9 H 10 i 11 1 12th m 0.1 0.1 0.05 0.05 0.05 0.21 0.25 0.28 0.25 0.28 no no no no no 20th 20th 20th 20th 20th 34 26th 26th 32 29 70 70 70 70 70

η
0.1

0.25
no

20th 30th 70

- 14 -

The examples given in the table were as follows Connections used:

a) CH-COO-

Br

b) CH-COO ^ Ο

OOC-CH,

CH.

c) ^C ₁₇ ^H 3 ₅ - ^COO - <O

d) ^C ₁₇ ^H ₃₅ - ^CO °

^CH

O VoOC-C ₁₇ H ₃₅

CH.

C I CH.

^OOC - ^C 17 ^H 33 ^Br 2

c _i8 h ₃₇ -coo- <O

809881/0927

Br

CH ₂ -CH-CH ₂ -O Br Br

CH-

C O

Br

0-CH ₀ -CH-CH ₀ ; 2,. 2

Br Br

^ Br

CH-

CH-

CH-

H ₂₃ Br ₂ -OH / ^ C iQy- ( CH,

H ₃₇ -O

CH

H ₂₃ Br ₂ ;

C ₁₈ H ₃₇ O

809881/0927

From the values given in the table it can be seen that it is the presence of the organic compounds of the general formula (I) or (II) in the foamable styrene polymers
made it possible to simultaneously obtain a number of desirable properties, such as:

- low moisture content of the foamable particles,
in any case approximately the same value as for particles which do not contain the products according to the invention;

- complete absence of odors during pre-shaming;

- short cooling time of the blocks;

- Block thickness shrinkage less than 1 %;

- high degree of sintering and

- fine-cell homogeneous structure.

809881/0927

Claims (6)

Patent claims: 1. Expandable polystyrene particles characterized in that they contain no more than about 1% by weight of at least one Compound of the general formula: .A -R. (D (II) wherein A = -0- or -COO-; and, when A = -0-: R ₂ and R-2, which can be identical or different, optionally halogen-substituted alkyl, cycloalkyl and / or phenyl groups; Rr is an alkyl group of about 4-30 carbon atoms or a wholly or partially halogen-substituted alkyl group having about 9-30 carbon atoms; X is a halogen or an optionally halogen-substituted alkyl group having 1 to about 8 carbon atoms; m is an integer from 0 to about 4; η is an integer from 0 to about 5; and R ^ and R ^, which may be the same or different, optionally Halogen-substituted alkyl groups with 1 to about carbon atoms mean, however, when Rg and R, Are alkyl groups, X = bromine and m = 2, R .. and R ^ are non-halogen-substituted Alkyl groups with 1 to about 30 carbon atoms or completely or partially halogen-substituted Mean alkyl groups of about 9-30 carbon atoms; 809881/0927 2826453 and if A = -COO-: R ^, R ^ and Rc, which can be the same or different, optionally halogen-substituted alkyl groups having 1 to about 30 carbon atoms; Rp and R ,, which can be identical or different, optionally halogen-substituted alkyl, cycloalkyl or phenyl groups; X is a halogen or an alkyl group having 1 to about 8 carbon atoms; m is an integer from 0 to about 4 and η is an integer from 0 to about 5,
contains. 2. Polystyrene particles according to claim 1, characterized in that at least one compound of the general Porrr.el (I) or (II) is present in an amount of from about 0.05 to 0.2% by weight. 3. Process for making foamable polystyrene particles according to claim 1, characterized in that the polymerization of styrene in the presence of a blowing agent and an amount of no more than about 1% by weight, based on the monomer, of at least one organic Compound of the general formula: .A -.R (D (II) wherein A, R ^, R2, R ^, R ^, Rc »X, m and η are those mentioned in claim 1 Have meanings is made. 809881/0927 - Jf- ³ 2826451 4. The method according to claim 3, characterized in that the compound of formula (I) or (II) in an amount from about 0.05-0.2% by weight, based on the monomer, is used. 5. The method according to claim 3-4, characterized in that at least one halogen-free compound of the general formula (i) or (il), wherein R ^, R ^ and R _{5 are} alkyl groups with more than 8 carbon atoms, is used as the organic compound . 6. The method according to claim 3-5, characterized in that styrene with at least one other vinyl and / or vinylidene compound, which is copolymerizable with styrene, is copolymerized in such amounts that a copolymer receives the at least 50 wt .-? o copolymerized Contains styrene. 809881/0927