AU629981B2 - Heat distortion resistant, expandable styrene polymers having a high capacity for expansion - Google Patents

Abstract

Expandable styrene polymers containing a) 80 to 99% by weight of polystyrene, b) 1 to 20% by weight of a styrene-soluble polymer having a softening temperature above 140 DEG C, c) 3 to 10% by weight, based on the sum of a) and b), of a C3- to C6-hydrocarbon as a blowing agent, and optionally d) conventional additives, in which the mixture of components a) and b) has a melt flow index MFI 200/5 of between 15 and 30, are distinguished by high heat distortion resistance and good expandability.

Description

629981 Form COMMONWEALTH OF AUST A PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority ,Related Art Name of Applicant S°Address of Applicant a 9 Actual Inventor Address for Service Address for Service BASF AKTIENGESELLSCHAFT D-6700 Ludwigshafen, Federal Republic of Germany KLAUS HAHN, UWE GUHR, HANS HINTZ, DIETMAR WITTENBERG WATERMARK PATENT TRADEMARK ATTORNEYS.

LOCKED BAG NO. 5, HAWTHORN, VICTORIA 3122, AUSTRALIA Complete Specification for the invention entitled: HEAT DISTORTION RESISTANT, EXPANDABLE STYRENE POLYMERS HAVING A HIGH CAPACITY FOR EXPANSION The following statement is a full description of this invention, including the best method of performing it known to us8 -1

V:

O.Z. 0050/41123 Heat distortion resistant, expandable styrene polymers having a high capacity for expansion o o q on 0 00a oa o 0 0000 a RO 0 0 of 0 0 o o oaa 00 0 0 0 0 0 0 0040 00 0 O 0 4 00 4 00 0 Foams based on a mixture of polystyrene and a polyrer having a high softening point have substantially higher heat distortion resistance than polystyrene foams.

However, products of this type have not attained any degree of industrial importance hitherto since economic processes for the preparation of corresponding expandable styrene polymers required for the production of foam moldings were unknown and, in addition, the products had unsatisfactory capacity for expansion.

It is an object of the present invention to develop expandable styrene polymers which are suitable for the production of heat distortion resistant foams and 15 which have a high capacity for expansion.

We have found that, surprisingly, this object is achieved by blowing agent-containing mixtures of polystyrene and a styrene-soluble polymer having a high softening point, if the blowing agent-free mixture of the polymers has a melt flow index MFI 200/5 of from to 20. Mixtures of this type can be obtained in a simple manner by the suspension polymerization of a solution of the polymer having a high softening point in styrene in the presence of a regulator.

25 The present invention accordingly provides expandable styrene polymers containing a) from 80 to 99 by weight uf polystyrene, b) from 1 to 20 by weight of a styrene-soluble polymer having a softening point above 140"C, 30 c) from 3 to 10 by weight, based on the sum of a) and of a C 3 to C,-hydrocarbon as blowing agent, and, if desired, d) conventional additives in effective amounts, the mixture cf components a) and b) having a melt flow index MFI 200/5 of from 15 to The present invention furthermore provides a process for tl preparation of expandable styrene 0 0G So 2 O.Z. 0050/41123 polymers of this type, which comprises dissolving component b) in styrene, polymerizing the solution in aqueous suspension in the presence of from 0.01 to 3 by weight, based on styrene, of a conventional regulator having a chain-transfer constant K of from 0.1 to 50, and adding the blowing agent and, if used, the additives before, during or after the polymerization.

The present invention also provides foams having a density of from 0.005 to 0.1 g/cm 3 and containing a) from 80 to 99 by weight of polystyrene and b) from 1 to 20 by weight of a s vrene-soluble polymer having a softening point abo 140"C, and, if desired, conventional additives in effective 1p 5. amounts, the mixture of components a) and b) having a melt flow index MFI 200/5 of from 15 to Surprisingly, the foams produced from the novel expandable styrene polymers have high dimensional stabila, O ity even at elevated temperature.

The novel products contain, as the principal component from 80 to 99 by weight, preferably from to 98 by weight, in particular from 90 to 97 by weight, of polystyrene.

The novel products furthermore contain, as component from 1 to 20 by weight, preferably from 2 to 15 by weight, in particular from 3 to 10 by 0" weight, of a styrene-soiuble polymer having a softening point above 140°C, preferably from 150 to 210 0 C, in particular from 160 to 200 0

C.

It is preferred that these polymers have suffi- 30 cient solubility in styrene for the amount of component b) required for the preparation of the novel products to be soluble in the corresponding amount of styrene. Examples of suitable polymers are poly-1,4-phenylene sulfide (softening point 190 0 poly-(2,6-dimethyl)-1,4-phenylene ether (softening point 200"C) and styrene-maleic acid (anhydride) copolymers containing from 10 to 49 by weight of maleic acid or maleic anhydride (softening 3 0.Z. 0050/41123 o ftf ft ft f rat, ft ft f f ft..

04 t ft ft f ft ft a o a ft f Ottf point 150 to 170"C).

It is essential to the invention that the blowing agent-free mixture of components a) and b) has a melt flow index MFI 200/5 (in accordance with DIN 53 735) of from 15 to 30, in particular from 17 to 28. If the MFI is below 15, the expansion capacity is unsatisfactory; a value above 30 means that the dimensional stability of the foams produced therefrom is inadequate.

The expandable styrene polymers contain, as blowing agent, from 3 to 10 by weight, preferably from 4 to 9 by weight, in particular from 5 to 8 by weight, based on the sum of a) and of a C 3 to C 6 hydrocarbon, such as propane, butane, isobutane, npentane, i-pentane, neopentane and/or hexane. Preference 15 is given to a commercially available pentane mixture.

The polystyrene particles may also contain other substances which provide the expandable product with certain properties. Examples :'-ich may be mentioned are flameproofing agents based on organic bromine or chlorine compounds, such as trisdibromopropyl phosphate, hexabromocyclododecane or chlorinated paraffin, and synergists for flameproofing agents, such as dicumyl peroxide and highly labile organic peroxides; furthermore antistatics, ,tabilizers, dyes, lubricants, fillers and substances 25 which have an antiadhesive effect on prefoaming, such as zinc stearate, melamine-formaldehyde condensates or silica, and agents for reducing the demolding time on expansion, for example glycerol esters or hydroxycarboxylates. The additives may be homogeneously distri- 30 buted in the particles or in the form of a surface coating, depending on the intended action.

Other suitable additives are styrene-soluble styrene-acrylonitrile copolymers, which, in small amounts, prevent shrinkage of the foams. If the amount added is increased, the foams have high oil resistance.

The expandable styrene polymers have a high expansion capacity E of from 30 to 80,preferably from ,k ft.

'ftr S. tf f ft S i i i g ,:3

P

f L_ 4 O.Z. 0050/41123 09 4 8 o 8 8 a 8 4 8 a 0908 to 80, in particular from 50 to 80, E being the ratio between the bulk density of the expandable beads to the bulk density of the foam beads obtained by steam treatment (6 minutes at 120"C).

The expandable styrene polymers also have a ratio between the expansion capacity E and the amount of blowing agent M moles of blowing agent per kg of pre-Fe sto styrene polymer) of from 30 to 80, preferably from to 80, in particular from 50 to 75. The novel products thus contribute to environmental protection, since significantly smaller amounts of blowing agent than in the prior art are required to achieve the same density.

In a preferred process, the blowing agent-containing styrene polymers according to the invention are 15 prepared by polymerizing a solution of component b) in styrene in aqueous suspension, the above-described blowing agents and, if used, the additives being added before, during or after the polymerization. It is also possible to dissolve mixtures of component b) with polystyrene, as is sometimes the usual commercial form, in styrene. During the polymerization, advantageously at a styrene conversion of from 20 to 90 from 0.01 to 3 by weight, preferably from 0.05 to 2 by weight, in particular from 0.1 to 1 by weight, of a conventional, 25 preferable bromine-free regulator having a chain-transfer constant K of from 0.1 to 50 are added.

The suspension polymerization of styrene is known per se and is described in detail in Kunststoff-Handbuch, Volume V (Polystyrol), Carl Hanser-Verlag, pages 679 30 to 688. In this process, styrene is suspended in water and conventional organic or inorganic suspension stabilizers are added, preferably in an amount of from 0.05 to 2 by weight, based on the suspension. The polymerization is generally carried out at from 80 to 130 0

C,

preferably from 100 to 120 0 C, and is initiated by organic polymerization initiators, for example peroxides or azo compounds, which decompose to form free radicals on 48 8 449' 4 8 8 4 4 8 44 1 4 1 5 O.Z. 0050/41123 exposure to heat. They are employed in an amount of from 0.01 to 1 by weight, based on the monomers. The chain transfer agents are generally added to the polymerization batch at a conversion of from 20 to 90 preferably from 40 to 60 For the purposes of the present invention, conversion is taken to mean the percentage of polymerized monomers, based on the total amount of monomers employed.

It can be measured, for example, by terminating the polymerization after a certain time, for example by adding inhibitors, and determining the amount of unpolymerized monomers.

The chain transfer agents used have a transfer constant K (measured by the method of Vollmert, GrundriB der Makromolekularen Chemie, Springer Verlag, 1962, o0 15 pages 52 and 71) of from 0.1 to 50, preferably from 1 004to 30, for example: n-dodecyl mercaptan (K 19) o tert.-dodecyl mercaptan (K 3) 0o 0 n-butyl mercaptan (K 22) tert.-butyl mercaptan (K 3.6) pentaphenylethane (K dimeric a-methylstyrene (K 0 The styrene content in the expandable styrene ,1 polymers should generally be low and should aeua41ykbe less than 0.2 by weight, preferably less than 0.1 by weight, in particular less than 0.08 by weight. In order to achieve this aim, it is expedient, when mercaptans are used as the regulator, to delay adding them until during the polymerization at a conversion of from 20 to The blowing agent-containing styrene polymer Pre-Pe-rs. '.j ;particles according to the invention are/in the form of H pF(-eRCC' k-L beads and ginerally have a diameter of from 0.2 to 4 mm.

They can be prefoamed by conventional methods for example using steam at above the softening point, to give foam particles having a diameter of from 0.5 to 2 cm and a density of from 0.005 to 0.1 g/cm 3 r ^r t- i 0, 6 O.Z. 0050/41123 o 0o o o 0o 0 0 0 004 0 0 0 000 0801 oa 00 00 0 0 0 0 00 0D O 0 0 9 It has been shown that this considerably increases the throughput through the added chain transfer agents., c.ornP\e' ev The prefoamed particles can then be expanded by conventional methods, ie. by heating in molds which do not close in a gas-tight manner, to give foam moldings having a density of from 0.005 to 0.1 g/cm 3 The addition of chain transfer agents affects the molecular weight and the molecular weight distribution of the resultant polymers, and thus also their rheological properties, which are in turn responsible for the capacity for expansion of the blowing agent-containing polystyrene particles and the dimensional stability of foam moldings produced therefrom. Thus, for example, a reduction in the melt extensibility results in a better 15 expansion capacity, and a reduction in the reversible elongation at the same melt extensibility results in improved dimensional stability. Both properties can be measured directly on the blowing agent-containing styrene polymer particles by a procedure in Prifung hochpolymerer Werkstoffe, Carl Hanser Verlag, Vienna, 1977, page 422.

The products according to the invention generally have, measured by the method described, a melt extensibility of less than 4.2.10 5 [Pas], preferably from 1.5 to 3.0.106 [Pas], and a reversible elongation of less than 0.95, preferably from 0.6 to 0.9.

The novel foams have high heat distortion resistance, and are generally dimensionally stable even at above 100"C, in some cases even up to 120 0

C.

In the examples, parts are by weight.

30 EXAMPLES 1 TO 29 1. Polymerization A mixture of 200 parts of water, 0.1 part of sodium pyrophosphate, 0.15 part of tert.-butyl perbenzoate, 0.45 part of benzoyl peroxide, 100 parts of a styrene solution containing the amounts given in the table of styrene, polystyrene, polymer b) and, as regulator, divinylbenzene, 7 parts of pentane.and 3 parts of 0040 0 0 4, 04 0000 o o a.

0 a t 4 0r 0 a 00 t 1 7 O.Z. 0050/41123 o 0 4 4'4 4 0 0* 00006 44 44 o0 o o 0 04 0B 0404D a 10 strength aqueous solution of polyvinylpyrrolidone was heated to 90°C with stirring in a pressure-tight stirred reactor, kept at 90"C for 5 hours, and subsequently heated at 100°C for 2 hours and at 120°C for a further 2 hours. The regulator used was tert.-dodecyl mercaptan. The components were added in the amounts given in the table, based on the styrene solution, and at the point in time given in the table.

After cooling, the bead polymer obtained, having a mean bead diameter of 0.8 mm, was separated from the aqueous phase, washed and dried.

2. Product properties a) Melt flow index The melt flow index MFI 200/5 was determined by the procedure of DIN 53 735 on a degassed sample freed from blowing agent.

b) Molecular weight measurement The mean molecular weights M, (weight average) and the molecular weight distribution were determined by the GPC method using polystyrene as the standard. A column combination was assembled ensuring best-possible resolution both in the low-molecularweight and high-molecular-weight ranges.

The column combination comprises 5 silica columns 25 as follows, each with a length of L 300 mm and an internal diameter D 10 mm: 1 x Si 1 x Si 100 1 x Si 300 30 1 x Si 1000.

The packing comprises LiChrospher and LiChrosorb from Merck (silica gels) having a grain size of Am (with the exception of Si 60 LiChrosorb).

The flow rate is 2.8 ml/min, and the solvent is tetrahydrofuran. 200 il of a 0.5 strength solution were injected at room temperature. The detector installed is a differential refractometer from 4 0 00 4* 44< c 1t h. 8 O.Z. 0050/41123 Knauer, dual detector type 61.00. A drop counter is used to ensure a uniform flow rate.

In order to convert the measurements obtained to the molecular weight, a calibration curve is produced in parallel from 12 narrowly distributed polystyrene samples from Pressure Chemical Co.

having known molecular weights.

In order to standardize the column combination used, the broad polystyrene sample No. 706 characterized by the National Bureau of Standards is measured, giving the following means for its molecular weight: M 74,000 H; M, 243,000 Mn 392,000 *ct The products according to the invention generally have a mean molecular weight M, of greater than 60-103 and less than 180.103, preferably from 100.103 to 180.103, in particular from 120.103 to 175-103.

The gradient of the high-molecular-weight edge of the molecular weight distribution curve is characterized by the difference between the means Mn+ -Mn, as described by H.G. Elias in Makromolekle, Huttig- Verlag, 1971, pages 52 and 64. In the case of the products according to the invention, the value for is generally less than 160.103, preferably less than 150.103, in particular less than 130.103 c) Bulk density As a measure of the capacity for expansion (6 minutes at 120 0 the bulk density was measured using a sieve (mesh width: 0.1 0.2 mm) measuring 1000 x 800 x 250 mm with a metal frame in a sealed metal housing with steam inlet and extractor.

The steam at 120 0 C passed into the prefoaming apparatus from below, passed through the wire fabric containing the products to be tested and escaped again through the steam extractor. Before commencing 9 O.Z. 0050/41123 the tests, the apparatus was first preheated for about 5 minutes. 100 g of the expandable bead polymers were subsequently distributed uniformly on the wire fabric, the apparatus was sealed and the steam valve was opened. After 6 minutes, the steam valve was closed again and the metal housing was opened. The bulk density was subsequently determined on the prefoamed material.

d) Throughput during prefoaming The bead polymers coated with 0.4 part by weight of glycerol monostearate were prefoamed to a bulk density of 15 g/l in a continuous stirred prefoamer, Rauscher type, using flowing steam, and the throughput was determined.

e) Heat distortion resistance After interim storage for 24 hours, the prefoamed foam particles were welded in a block mold, Rauscher t r type, by steam treatment at a pressure of 1.8 bar to give a block with a density of 15 g/l.

The heat distortion resistance was determined on samples of the foam block in accordance with DIN 53 424 (Bestimmung der Formbestandigkeit in der Warme bei Biegebeanspruchung und bei Druckbeanspruchung).

The results are shown in the table.

j 2: a a a, -r a a.t 0 0 t 0O a at 0 a a 00 wO a 00 000 4 00 000 0i 0 0 0 0~ 0 aI 00 90 0 s 0 0 0 0ee Table Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 (comp.)(comp.) Styrene by wt.] Polystyrene by wt.] Polymer b by wt.] Divinylbenzene by wt.] tert-Dodecyl mercaptan by wt.] Point of addition convers.] MFI 200/5 min] K .10 3 M+,-M-103 Bulk density [g/1] Throughput [kg.h] Heat distortion resistance 90 90 95 95 95 90 90 90 95 95 95 95 90 90 2 2 1 1 1 2 2 2 1 1 1 1 2 2 2 8A 8A 4A 4A 4A 8A 8A 8A 4A 4AS 4A 8A 8A 8A 0.01 0.01 0.01 0.03 0.03 0.1 0.01 0.01 0.5 0.5 0.8 0.01 0.1 0.1 0.01 0.2 0.2 0.01 0.5 0.5 0.8 40 40 40 40 40 40 40 0 0 0 0 0 0 10 9 20 18 22 24 23 26 19 18 20 19 23 22 24 191 173 35.4 190 176 36.1 168 141 23.4 174 147 24.3 157 122 19.2 141 114 14.9 147 119 15.2 128 103 13.9 171 142 23.8 174 149 24.1 161 128 19.5 163 132 19.0 144 111 14.9 149 120 14.9 138 108 14.0 51 48 81 80 92 99 97 110 85 82 95 91 98 96 108 115 120 107 110 109 114 119 118 107 110 106 110 113 115 113 A poly(2,6-dimethyl)-1,4-phenylene ether B poly-1,4-phenylene sulfide C styrene-maleic anhydride copolymer containing 15 by weight of maleic anhydride

-A

I

Table (continuation) Example 16 17 18 19 20 (comp. comp.) 21 22 23 24 25 26 27 28 29 Styrene [96 by wt-] Polystyrene by wt.) Polymer b) by wt-] Divinylbenzen.,-' [96 by wt.] tert-Dodecyl mercaptan by wt-] Point of addition convers.] MFl 200/5 min] A* .10 3 I0 Bulk density [g/1l] Throughput [kg. h] Heat distortion resistance 0

C]

90 90 94 94 94 94 90 90 90 90 90 90 90 2 2 1.2 1.2 1.2 1.2 8A 8A 4.8B 4.8B 4-8B 4.8B 2 2 2 2 2 8B 8B 8B 8B 10C IOC 0.01 0.01 0.01 0.01 0.01 0.01 0.8 1.0 0 0 0.1 0.1 0.1 0.1 0.5 0.5 0.8 0.01 0.01 0.3 40 40 40 40 40 40 40 23 27 14 13 20 19 18 17 25 24 27 9 8 19 141 110 141 124 101 13.7 210 163 29.9 220 169 30.8 161 142 24.0 166 146 24.5 170 149 25.9 172 151 26.2 139 111 14 .3 144 109 14.5 121 101 13.4 198 169 29.9 194 171 30.5 135 i11 15 .8 105 112 63 61 90 88 89 85 101 98 112 65 61 116 112 112 114 111 114 116 118 115 118 115 112 114 113

Claims (3)

1. 4. 4, 1. An expandable styrene polymer containing a) from 80 to 99 by weight of polystyrene, b) from 1 to 20 by weight of a styrene-soluble polymer having a softening point above 140°C, c) from 3 to 10 by weight, based on the sum of a) and of a C 3 to C 6 -hydrocarbon as blowing agent, and, if desired, d) conventional additives in effective amounts, the mixture of components a) and b) having a melt flow index MFI 200/5 of from 15 to 2. An expandable styrene polymer as claimed in claim 1, containing, as component from 1 to 20 by weight of poly-1,4-phenylene sulfide. 3. An expandable styrene polymer as claimed in claim 1, containing, as component from 1 to 20 by weight of poly-(2,6-dimethyl)-1,4-phenylene ether. 4. An expandable styrene polymer as claimed in claim 1, containing, as component from 1 to 20 by weight of a styrene-maleic acid (anhydride) copolymer containing from 10 to 49 by weight of maleic acid (anhydride). A process for the preparation of an expandable styrene polymer as claimed in claim 1, which comprises dissolving component b) in styrene, polymerizing the solution in aqueous suspension in the presence of from 0.01 to 3 byweight, based on styrene, of a conventional regulator having a chain-transfer constant K of from 0.1 to 50, and adding the blowing agent and, if used, the additives before, during or after the polymerization.
2. 6. A foam having a density of from 0.005 to 0.1 g/cm 3 and containing a) from 80 to 99 by weight of polystyrene and b) from 1 to 20 by weight of a styrene-soluble polymer having a softening point above 140"C, and, if desired, conventional additives in effective amounts, the mixture of components a) and b) having a 13 O.Z. 0050/41123 melt flow index MFI 200/5 of from 15 to
3. 7. A process for the preparation of a foam as claimed in claim 6, which comprises expanding an expand- able styrene polymer as claimed in claim 1 in particle form by heating to above the softening point, and welding the resultant foam particles to one another by heating in a mold which does not close in a gas-tight manner. DATED this 20th day of September 1990. BASF AKTIENGESELLSCHAFT a o S..o eWATERMARK PATENT TRADEMARK ATTORNEYS c a "THE ATRIUM" 0 290 BURWOOD ROAD E' a HAWTHORN. VIC. 3122. g t a; a a i