CH662815A5 - METHOD OF PREPARATION OF POLYMERS styrenic MODIFIED RUBBER. - Google Patents

Description

662815

2

CLAIM

Process for the preparation of styrenic polymers modified by rubber, exhibiting good cracking behavior under stresses and good behavior at low temperatures, characterized in that a solution of a rubber in styrene is mass polymerized in which the rubber is an anionic polybutadiene having a proportion of 1-2 vinyl isomer of between 10 and 12%, a high molecular weight at least equal to 300,000 and a viscosity greater than or equal to 140 mPa-s, for a solution of 5 % in styrene, the solution containing between 7 and 10% by weight of rubber and the polymerization being carried out in the presence of the dimer of α-methyl-styrene or of a compound chosen from n-dodecylmercaptan, tertiododecylmer-captan , 1,3-diphenyl butadiene, cis-diphenylcyclobutene, trans-diphenylcyclobutene, methylphenylindane, diphenylcyclo-butane or the mixture of two or more of these compounds, used in an amount at least equal e at 0.08% and at most equal to 0.3% by weight relative to the total weight of all the constituents, in the presence of cyclohexane and isoparaffinic hydrocarbons or ethylbenzene, used at least in an amount equal to 7% by weight, relative to the total weight of all the ingredients contained in the solution and in that 0.5 to 1% by weight is used relative to the weight of all the ingredients of the solution of a selected additive, among a mono and / or a di and / or a triglyceride of stearates or their mixture among polyethylene waxes, among additives containing the polyethylene glycol function or among additives based on silicone oil.

The present invention relates to a process for the preparation of molding materials based on polystyrene. It relates more particularly to a process for preparing impact polystyrene having improved resistance to cracking under stresses and / or in contact with corrosive agents.

It is known that molded parts formed from styrene polymers crack under stress when they are brought into prolonged contact with chemical agents which trigger this corrosion phenomenon. These agents are in particular oils and greases as well as halogenated organic blowing agents such as freon. This corrosion manifests itself in practice both in packaging for edible fats and in the manufacture of impact polystyrene refrigerators: in the latter case, the refrigerator cells crack during the expansion of the polyurethane, by means of a blowing agent such as freon. This poor behavior of the shock polystyrene is all the more annoying that the attack of the freon occurs when the refrigerator is already finished, which requires either to dispose of the refrigerator, or to carry out disassembly and expensive assemblies .

To solve this problem, it has been proposed to coat the walls of refrigerators in contact with freon with a freon-resistant film, such as the acrylonitrile-butadiene-styrene (ABS) terpolymer. However, such a protection system causes a sharp increase in costs. It has also been proposed to replace part of the ABS with polyethylene films. Unfortunately, it is very difficult to obtain good adhesion of these two thermoplastics. It has also been proposed to increase the resistance to cracking by the subsequent addition of another rubber. Unfortunately, there are poor improvements even with the use of large amounts of rubber.

We have now found a way to manufacture molding materials which exhibit good cracking behavior under stresses and / or in contact with corrosive agents.

The object of the present invention is therefore the method defined in the claim.

The use of said additives facilitates the manufacture of polymers. Preferably, these additives are added after the polymerization, for example in internal mixers.

The implementation of the process which is the subject of the invention makes it possible to obtain polymers which not only have good impact properties, but which are especially not very sensitive to cracking under stresses and / or in contact with corrosive agents and also exhibiting good behavior at low temperatures below 0 ° C. All of these properties allow their use without additional protective treatment in the construction of tanks and storm doors of refrigerators and freezers, as well as for the manufacture of elements of kitchen or bathroom furniture trim, called to be cleaned frequently by detergents. Their resistance to corrosive agents also allows their use in the manufacture of tide cases used in particular for the transport of fish, as well as in the manufacture of food packaging, in particular fat.

The implementation of the process according to the invention makes it possible to obtain polymers which have a swelling index greater than 10. This swelling index is determined by dissolving the polymer obtained in toluene, then centrifuging and decanting the solution. The solid fraction obtained is weighed in the wet state then dried and reweighed. The swelling index is by definition the ratio:

j _ Weight of wet gel Weight of dry gel

This index actually expresses the degree of crosslinking of the rubber. It should be considered as an inverse of weight concentration and therefore the higher the swelling index, the lower the degree of crosslinking of the rubber.

The process of the invention leads to polymers which have a gel content greater than 30. This gel content expresses the proportion of rubber and it is given by the following relationship reduced to 1 gram of polymer:

Another characteristic of the polymers obtained according to the process of the invention is that the average diameter of the particles of the dispersed rubber phase, observed according to the technique of electron microscopy described by KATO in J. Electro. Microphones. 14, 19865 (20), is greater than 8 and at most equal to 13 microns; this diameter is determined according to the methods described by CRAIG [J. Polym. Sci. Polym. Chem. Ed. 15, 433 (1977)] and JAMES [Polym. Eng. Sci. 8, 241 (1968)]. These measurement methods make it possible to evaluate the average size of the elastomer nodules dispersed in the polystyrene matrix, as well as the distribution of the particle size. The most commonly used device for evaluating the size and polydispersity of sizes of the elastomer globules dispersed in the styrenic matrix is the “COLOR” counter sold by the company COULTRO-NICS.

The process of the invention results in a polymer having the particularity of having only one glass transition of the elastomer phase, this glass transition being measured according to known methods of viscoelasticimetry and adjusted to values less than or equal to - 80 °. C. The polymer obtained has no secondary transition between —70 ° C. and 0 ° C. The measurement of the glass transition is carried out on a RHEOVIBRON DDV - IIC viscoelasticimeter or METRAVIB viscoelasticimeter [the measurement methods are described by NIELSEN in MECHANICAL PRO -PERTIES OF POLYMER AND COMPOSITES, 2nd volume, 1974, Marcel DERKER Inc. NY, and also by J. BOYER, Macromol. Sci. Phys. B 9 (2) 187 (1974)]. According to the invention, the glass transition spectrum of the rubbery phase is spread over a certain temperature range corresponding to a frequency range characteristic of the frequencies of high speed shocks.

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662,815

According to the invention, a solution of a rubber in styrene is mass polymerized using a rubber consisting of anionic polybutadiene having a molecular mass of between 300,000 and 400,000 and a viscosity greater than 140 mPa • s and less at 220 mPa • s, the viscosity being determined by dissolving 5 parts by weight of the rubber in 95 parts by weight of styrene. The use of rubber having a viscosity greater than 220 mPa ■ s leads to a too viscous solution, difficult to handle and to process industrially, the use of rubber having a viscosity less than 140 mPa • s leading to a polymer having nodules with too small a particle size very much less than 10 microns. According to the invention, the amount of rubber used is between 7 and 10% by weight relative to the amount of styrene used. The use of an amount greater than 10% leads to too elastic polymers having poor mechanical properties and devoid in particular of rigidity. According to the invention, the term “anionic polybutadienes” means rubbers produced by a “anionic” type process.

According to another characteristic of the invention, the polymerization is carried out in the presence of the dimer of α-methyl-styrene or of a compound chosen from n-dodecylmercaptan, tertiododecylmer-captan, 1,3-diphenyl-butadiene, cis-diphenylcyclobutene, trans-diphenylcyclobutene, methylphenylindane, diphenylcyclobutene or the mixture of two or more of these compounds, used in amounts of between 0.08 and 0.3% relative to the total weight of the solution.

According to another important characteristic of the process of the invention, the polymerization is carried out in the presence of cyclohexane, isopar or ethylbenzene used in an amount at least equal to 7% by weight relative to the total weight of the solution. According to the invention, depending on the nature of the solvent used, different and preferential quantities are used: 8% for ethylbenzene, 10% for cyclohexane and 13% for isopar which is a commercial product consisting of hydrocarbons isoaliphatic (Cf. CONDENSED CHEMICAL DICTIONARY, Rose RHEINHOLDT). According to another important characteristic of the process of the invention, the polymerization is carried out in the presence of 0.5% and 1% by weight relative to the total weight of an additive chosen from a mono- and / or a di- and / or a stearate triglyceride or a mixture thereof, among polyethylene waxes, among additives containing the polyethylene glycol function or among additives based on silicone oil. The di and / or triglycerides of stearates are compounds having a melting point of about 60 ° C, a flash point above 150 ° C; they are sold for example under the brand ATMOS 150 by the company ICI AMERICA Inc. Polyethylene waxes are polycires sold by the company HÜLS. Polyethylene waxes are products with a drop point of between 70 and 80 ° C, a density of 0.86-0.88 and an average molecular weight of about 2,500; they are sold for example by the CDF CHIMIE Company. Silicone waxes are products soluble in most organic solvents; they are sold under the brand DOW CORNING 200 FLUID by the company DOW CORNING. The use of such additives facilitates the subsequent processing of the polymers obtained as well as the properties of the finished products. Preferably, these additives are added after the polymerization in internal mixers; using for example a mixer type GH 5 sold by the company WERNER-PFLEIDERER. The adjustment of the melt index is obtained by the incorporation of 1 to 3% of plasticizers, in particular consisting of liquid paraffin; the measurement of the melt index is determined according to standard ASTM D 1238.

For the implementation of the process of the invention, the polymerization can be carried out using known techniques. The autoclave used is equipped with an agitator, a heating device and a cooling system. All reagents used as well as additives are chemicals used in mass polymerization processes; antioxidants such as 2,6 ditertio-butyl paracre-sol, 2,2 methylene bis 4 (methyl-6-tertiobutylphenol), octadecyl-3- (3,5-di-ter-butyl-4-hydroxyphenyl) propionate, tri (2 methyl) -4

hydroxy-5 tert-butyl phenol) butane, triethylene glycol-bis 3- (3 tert.-butyl-4 hydroxy 5-methyl phenyl) propionate or mixtures of phenolic antioxidants and polymerization initiating phosphates such as benzoyl peroxide, or ditertiobu-tyle peroxide, cyclohexane peroxide or tert-butyl peroxy isopropyl carbonate or dicumyl peroxide or tert-butyl perbenzoate. All of these additives are preferably used in small quantities: for example, at most 0.5% by weight relative to styrene with regard to the antioxidants, at most 0.3% by weight relative to styrene for the peroxides, which are used alone or as a mixture. It is also possible to add other conventional additives such as paraffin oils in an amount at most equal to 5% by weight relative to styrene: the use of such compounds makes it possible to obtain polymers having both good thermal and rheological properties and also allows easy processing of the polymers obtained.

In a preferred embodiment of the process, all the reagents, with the exception of peroxides, are introduced into the autoclave and heated with stirring at a temperature in the region of 40 ° C. for three hours, so as to dissolve the rubber in other reagents. After this step of dissolving the rubber, the mixture is heated to a temperature between 80 and 250 ° C., for a period of approximately 8 hours. After polymerization, the polymer obtained is subjected to a heat treatment, then devolatilized and granulated.

The following examples illustrate the present invention. All quantities are expressed in parts by weight.

Example 1

A reactor used for mass polymerization, equipped with a stirring system, a heating device and a cooling system, is responsible for:

- 83.30 parts of styrene,

- 7.5 parts of polybutadiene rubber obtained by an anionic process and having the particularity of a vinyl isomer 1-2 ratio between 10% and 12%, having a molecular weight of 350,000 and a viscosity of 190 mPa • s for a solution at 5% by weight, in styrene,

- 0.15 part of a-methyl-styrene dimer,

- 8 parts of ethylbenzene,

- 1 part of paraffin.

Then added 0.05 part of an antioxidant consisting of octadecyl 3- (3,5 di-ter-butyl-4 hydroxy-phenyl) propionate. The reaction mixture is then subjected to heating in stages so that its final temperature reaches 145 ° C. after 7 h 50.

After this heating phase, 80 parts of solid material are obtained which are treated hot for 1 h 50. After devolatilization, which consists in subjecting the polymer to a heat treatment at a temperature between 200 and 240 ° C. under a vacuum of 970-985 mbar, the polymer is granulated. Its characteristics are summarized in the table below:

- The VICAT point is measured according to DIN 53460.

- The fluidity index is determined according to standard ASTM D 1238.

- The impact resistance is evaluated by implementing the ASTM D 256 standard.

- The gel content is calculated by stirring in cold toluene the polymer obtained, then by centrifuging the whole, which makes it possible to determine the amount of gel insoluble in toluene. The dry mass of the insoluble polymer is determined by treating the gel obtained previously under vacuum: the percentage of gel relative to the test portion expresses the rate of gel.

- The swelling index is equal to the ratio of the mass of gel to the dry resin.

- The particle size is determined according to the KATO technique, already mentioned above, using the methods of JAMES, already mentioned above.

- The tensile strength is determined according to DIN 53455.

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662,815

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- The resistance to corrosion by cracking under stress is determined according to standard AGK 31, which is a standard resulting from a working group made up of manufacturers of refrigerators and thermoplastics; this standard expresses, for an injected test piece, the percentage remaining at elongation under a stress of 75 kg / cm2; the remaining percentage must not be less than 75% in the case of halogenated hydrocarbon (freon) when the test piece is injected; the percentage must not be less than the remaining 50% when the test piece is prepared by extrusion; finally, this remaining percentage must not be less than 40% when the test piece is compression molded.

Example 2

Example 1 is repeated, but using 81.08 parts of styrene, 10 parts of ethylbenzene, 6.85 parts of the same polybutadiene rubber used in Example 1, 0.1 part of the dimer of α- methyl styrene and 1.97 parts of paraffin oil: the properties of the polymer obtained are summarized in the table below.

Example 3

Example 2 is repeated, but using 80.98 parts of styrene, 0.2 part of the dimer of α-methyl-styrene instead of 0.1. The properties of the polymer obtained are summarized in the table below.

Example 4

Example 1 is repeated using:

79.18 parts of styrene,

11 parts of ethylbenzene,

0.15 part of a-methyl-styrene dimer,

3.83 parts of paraffin oil,

5.8 parts of fully anionic polybutadiene rubber, 0.042 part of octadecyl-3,3,5 di-ter-butyl-4 hydroxyphenyl pro-pionate.

The properties of the polymer obtained are summarized in the table in the appendix.

Example 5

Example 1 is repeated using:

82.9 parts of styrene,

7.5 parts of ethylbenzene,

0.10 part of a-methyl-styrene dimer,

2.3 parts of paraffin oil,

I part of mixture of glycerol mono- and distearate,

6.2 parts of polybutadiene.

The properties are summarized in the attached table.

Example 6

Example 1 is repeated by implementing:

78.06 parts of styrene,

6.82 parts of rubber,

13 parts of isopar,

0.15 part of a-methyl-styrene dimer,

1.97 parts of oil,

0.5 part of mixture of mono- and glycerol distearate. The properties are summarized in the table.

Example 7

Example 1 is repeated by implementing:

79.18 parts of styrene,

0.042 parts of antioxidant sold under the brand IRGA-NOX 1076,

3.83 parts of paraffin oil,

5.8 parts of anionic polybutadiene,

II parts of ethylbenzene,

0.10 part of a-methyl-styrene dimer,

0.042 parts of octadecyl-3,3,5-di-ter-butyl-4 hydroxyphenyl pro-pionate.

Example 8

Example 1 is repeated using:

83.69 parts of styrene,

7.5 parts of ethylbenzene,

5 0.083 part of a-methyl-styrene dimer,

1.91 parts of paraffin oil,

0.5 part of polyethylene waxes having an average molecular weight of 2500, a viscosity of 60 to 100 mPa • s at 120 ° C, a density of 0.86 and a drop point of between 70 and 80 ° C, 10 6.82 parts of anionic polybutadiene.

The properties are summarized in the attached table.

Example 9 (comparative example)

The product is obtained with the following amounts of reactants: 83.69 parts of styrene,

7.5 parts of ethylbenzene,

6.82 parts of polybutadiene consisting of a mixture,

50-50 of anionic polybutadiene (10-12% of vinyl 1,2) and of ZIEGLER polybutadiene (97% of the isomer 1-4 eis) instead of an anionic polybutadiene alone,

0.073 part of a-methyl-styrene dimer,

1.91 parts of paraffin oil.

Example 10

A polymer is prepared from the following ingredients: 83.69 parts of styrene,

7.5 parts of ethylbenzene,

6.82 parts of polybutadiene rubber obtained by an anionic process and having a level of 1-2 vinyl isomer of between 10 and 12%, having a molecular weight of 350,000 and a viscosity of 190 mPa • s for a solution of 5 % by weight in styrene,

0.083 part of the dimer of α-methyl-styrene,

1.91 parts of paraffin oil,

35 0.5 parts of synthetic wax having a melting point of 140 ° C. and sold under the brand NOPCOWAX 22 DS by the company DIAMOND SHAMROCK.

The properties of the polymer obtained are summarized in the attached table.

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Example 11

Example 10 is repeated, but by replacing the synthetic wax with 1 part of a wax sold under the brand POLYWAX 2000 by the company HÜLS.

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The properties of the polymer obtained are summarized in the attached table.

Example 12

Example 10 is repeated, replacing the NOPCOWAX 22 DS waxes with a part of polyethylene wax having an average molecular weight of 2500, a viscosity of 60 to 100 mPas at 120 ° C., a density of 0.86 and a drop point between 70 and 80 ° C. The properties of the polymer obtained are summarized in Table J5 appended.

Example 13

Example 10 is repeated, substituting 0.5 part of wax for 1 part of silicone oil sold by the company DO \ ^ CORNING under the 6Q mark DOW CORNING 200 FLUID.

The properties of the product obtained are indicated in the attached table.

Example 14

Example 10 is repeated, replacing the silicone oil with 0.5 part of “800” solid polycires sold by the company HÜLS.

The properties of the product obtained are indicated in the attached table.

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Comparative test 15

A polymer is prepared from:

83.70 parts of styrene,

7.5 parts of ethylbenzene,

0.073 parts of a-methyl-styrene dimer, 5

1.91 parts of paraffin oil,

6.82 parts of anionic polybutadiene composed of 11% of 1-2 vinyl isomer and having a solution viscosity of 95 mPa • s and a weight average molecular weight of 273,000.

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Example 16

We implement:

81.03 parts of styrene,

10 parts of ethylbenzene,

6.85 parts of the same polybutadiene rubber of 15

example 1,

0.10 part of a-methyl-styrene dimer,

1.97 parts of paraffin oil,

0.05 part of antioxidant based on octadecyl 3- (3,5 di-ter-butyl-4 hydroxy phenyl) propionate, 20

0.5 part of mixture of mono- and glycerol distearate.

Example 17 We use:

81.03 parts of styrene, 25

10 parts of ethylbenzene,

6.85 parts of the same polybutadiene as Example 1,

0.10 part of a-methylstyrene dimer,

1.97 paraffin oil,

0.5 part of silicone oil.

Example 18

Example 1 is repeated, but replacing the α-methyl-styrene dimer with a mixture of 1,3-diphenyl butadiene, cis-diphenyl-cyclobutene, trans-diphenylcyclobutene, methylphenylindane and diphenylcyclobutane. The properties of the polymer obtained are summarized in the attached table.

The following abbreviations have been taken from the attached table:

- R.T.: Tensile strength

- M .: Module

- C.R.: Stress at break

- C.S.: Threshold stress

- A.R.: Elongation at break

- a.r. : Elongation remaining

- E.E.: Extruded test tubes

- E.M.: Molded test pieces

- The oil hold was made with "LIVIO olive oil

- The extruded test pieces had the dimensions 200 x 20 x 2 mm The resistance to corrosion by cracks under stresses is expressed by the remaining elongation at break, in% defined by the relationship:

Remaining elongation% =

Elongation of tensile break after contact with freon or oil Elongation of initial tensile break

Example

VICAT point (1 kg-120 ° C / h) (° C)

Fluidity index (g / 10 ')

Izod impact resistance compressed test pieces (kg x cm / cm)

Freeze rate (%)

Swelling index

Granulo-

metrics (microns)

R.T. on E.E. (withdrawal rate 10%)

M

(kg / cm2)

C.S. (kg / cm2)

C.R.

(kg / cm2)

1

100.0

4.6

6.9

35.0

11.8

12.7

9480

153

185

2

100.5

5.4

7.0

34.6

10.9

8.0

9,990

145

183

3

100.0

6.5

6.9

34.8

11.4

10.1

9100

130

169

4

94.0

11.1

6.8

32.6

12.1

9.5

9170

123

156

5

101.0

5.0

8.0

35.0

12.0

7.5

10,000

140

160

6

101.0

4.5

7.0

35.0

11.9

7.5

10,500

153

7

95.0

9.5

7.2

33.0

12.2

8.5

9200

129

154

8

101.0

5.5

7.0

34.0

11.0

7.0

10110

134

156

9

102.0

4.4

6.9

32.7

9.5

4.0

11000

179

182

10

100.5

5.0

6.5

11975

161

155

11

99

6.0

6.5

11,840

177

169

12

100

6.0

6.5

11,800

160

170

13

100.5

6.5

6.0

11800

164

162

14

99.5

6.5

6.0

11500

170

175

15

101

4.5

3.0

11000

175

190

16

99.0

6.0

7.0

35

11

8.5

10,000

140

185

17

100.0

6.2

6.5

33

11

8.5

10100

142

185

18

100.0

5.5

6.7

34.1

12

18.6

10,050

140

170

Example

Freon resistance 11 on E.E. (a = 75 kg / cm2) (a.r.%)

Resistance to oils on E.E. (a.r.%)

R.T. on E.M. by compression

Freon resistance on E.M. by compression (a = 75 kg / cm2)

A.R.

(%)

a.r.

after 40 min (%)

a.r.

after 50 min (%)

a.r.

after 30 min (%)

a.r.

after 50 min (%)

M

(kg / cm2)

C.S.

(kg / cm2)

C.R.

(kg / cm2)

A.R.

(%)

a.r.

after 40 min (%)

a.r. after 50 min (%)

1

53

94

85

94

75

11830

125

135

32

94

78

2

54

81.5

74

81.5

79

10840

108

115

26

77

69

3

51

82

78

82

82

9860

102

117

29

82

72

4

59

100

98

100

88

12230

104

128

47

100

92

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Example

Freon resistance 11 on E.E. (cr = 75 kg / cm2) (a.r.%)

Resistance to oils on E.E. (a.r.%)

R.T. on E.M.

by compression

Freon resistance on E.M. by compression (<r = 75 kg / cm2)

A.R. (%)

a.r.

after 40 min (%)

a.r. after 50 min (%)

a.r. after 30 min (%)

a.r. after 50 min (%)

M (kg / cm2)

C.S.

(kg / cm2)

C.R.

(kg / cm2)

A.R.

(%)

a.r.

after 40 min (%)

a.r. after 50 min (%)

5

47

84

81

94

88

35

83

83

6

47

80

75

90

85

34

83

81

7

8

54 47

100 95

100 89

98

95

10980

104

125

51 30

75 79

74 76

9

34

15

12

10

5

30

15

10

10

55

52

47

11

54

54

60

12

55

66

64

13

55

57

50

14

50

50

40

15

40

10

3

10

4

16

50

87

87

90

83

17

52

82

79

80

79

18

50

60

60

75

70

12100

110

120

35

78

75

R