CH623842A5 - Arc-resistant composition - Google Patents

Description

The subject of the present invention is an arc-resistant composition containing an arylene polysulfide as a basic ingredient.

In many commercial applications involving the use of a high voltage electrical current, for example the transmission of electrical energy or electrical resistance heating, it is either necessary or advantageous to use components made of materials which resist the arc, as defined in standard ASTM-D495-73. Even more advantageous are compositions which are resistant to arc and water and which have acceptable physical properties.

The object of the present invention is to provide such a composition.

The arc-resistant composition according to the invention comprises an uncured or partially cured arylene polysulfide, and an amount of 20 to 50% by weight, relative to the total composition, of clay and / or talc as charge. Preferably, the composition comprises 30 to 60% by weight, relative to the total composition, of fillers, including clay and / or talc.

The arc-resistant composition, comprising an arylene polysulfide and a clay or talc filler, can also contain, as filler, from 0 to 35% by weight of glass and / or from 0 to 40% by weight of carbonate of calcium (the two weight percentages being calculated relative to the total weight of the composition) in the range of 30 to 60% by weight of total load. The presence of the glass increases the tensile strength of the composition.

An arc-resistant composition having better water resistance preferably comprises phenylene polysulphide, from 30 to 60% by weight of fillers comprising at least clay and / or talc and 0.5 to 5% by weight of silanes, all calculated relative to the total weight of the composition.

A preferred process for the preparation of the above-described composition is as follows: an uncured or partially cured phenylene polysulphide is placed in a suitable mixing apparatus with 30 to 60% by weight of fillers comprising 0 to 35% by weight of glass , 0 to 40% by weight of calcium carbonate and at least clay and / or talc. The ingredients are mixed until a homogeneous mixture is obtained. The mixture is then injection molded to form an arc-resistant composition.

According to a variant of this process, suitable for the preparation of an arc-resistant composition having better water resistance, an unhardened or partially hardened phenylene polysulfide is mixed in a tumbler with 30 to 60% by weight. fillers comprising 0 to 35% by weight of glass, 0 to 40% of calcium carbonate, 0.5 to 5% by weight of silanes, the remainder comprising at least talc and / or clay. The mixture is then pressure molded to form an arc-resistant composition having the desired shape.

Additive-free arylene polysulfides do not exhibit good arc-resistance properties. For example, phenylene polysulfide has an arc resistance of approximately 10 s, measured in accordance with ASTM-D495-73, while the minimum acceptable value for arc-resistant materials is approximately 120 s.

The arc-resistant composition according to the invention, that is to say it has an arc resistance equal to or greater than 120 s, measured according to standard ASTM-D495-73. Furthermore, it has been discovered that by adding small amounts of silanes to the present arc-resistant composition, it is imparted better resistance to water and decreases, or at least stabilizes, its coefficient of linear expansion.

For the implementation of the present invention, any uncured or partially cured arylene polysulfide can be used, whether it be a homopolymer, a copolymer, a ter-polymer, etc., or a mixture of these polymers . In this context, an uncured or partially cured polymer is a polymer whose molecular weight can be increased either by lengthening the molecular chain, or by crosslinking, or by combining the two and providing sufficient energy, for example heat , preferably in the presence of oxygen. The process which increases the molecular weight of the polymer is called the curing process. Arylene polysulfides having intrinsic viscosities, in chloronaphthalene (0.2 g of polymer in 100 ml of chloro-naphthalene) at 206 ° C, of at least about 0.08, advantageously between about 0.1 and 0.3 and preferably about 0.13 and 0.23 are particularly suitable for this invention. Examples of the polymers which can be used here are disclosed in US Patent No. 3354129. Other examples of arylene polysulfide are 4,4'-biphenylene polysulfide, 2,4-tolylene polysulfide, a copolymer of p-dichlorobenzene, 2,4-dichloro-toluene and sodium sulfide, as well as their mixtures. Of all the arylene polysulfides, phenylene polysulfides are currently preferred for use with the present invention.

Any clay, talc, calcium carbonate or glass that is commercially available can be used as fillers; these ingredients do not have to be extremely pure.

Although it is believed that any silane can be used to impart better water resistance and better coefficient of linear expansion to the present resistant composition

5

10

15

20

25

30

35

40

45

50

55 '

60

65

3

623,842

at the arc, the alkylsilanes, the alkoxysilanes and their polymers are currently preferred. Examples of these are γ-glycidoxy-propyltrimethoxysilane, methyltrimethoxysilane and polyisoxy-methoxysilane.

The proportion of fillers added to the arylene polysulfide can vary from approximately 30 to 60% by weight of the total composition. The fillers comprise 0 to 30% by weight of glass, 0 to 20% by weight of calcium carbonate, the balance being talc and / or clay. A currently preferred arc-resistant composition includes the following ingredients:

PSP 45% by weight Clay 17.5% by weight Talc 17.5% by weight Glass 20.0% by weight

The concentration of silanes which can optionally be incorporated into the present arc-resistant composition can vary from about 0.5 to about 5% by weight; usually it is between about 0.5 and 1% by weight of the total composition.

The process for preparing the present arc-resistant composition is best explained by following the sequence of process steps.

If the composition is prepared by injection molding, it is advantageous to partially cure the polymer in order to reduce its melt flow value to a value below 75 g / 10 min according to ASTM-D1238-74 (343 ° C and load of 5 kg). Polymers having a melt flow value below these values can be injection molded more efficiently. The curing process is carried out by subjecting the uncured or partially cured polymer, preferably in air, to elevated temperatures until the desired value of the melt flow is obtained. Normally, high temperatures of at least 260 ° C are used; the preferred temperature is 288 to 482 ° C.

The uncured or partially cured polymer is placed in a tumbler or other suitable mixer with previously selected amounts of one or more fillers and, optionally, a previously selected amount of silanes. The ingredients are put into composition according to a known process until a homogeneous mixture is obtained.

The mixture is then introduced into an injection molding apparatus to form, after treatment, an arc-resistant composition. The product of the injection molding step can be shaped into the desired shape during the injection molding, or it can be machined by machine or otherwise when the injection molding step is completed.

When the composition is not prepared by injection molding, but by a process such as pressure molding, the melt flow properties of the arylene polysulfide are normally less important. Any solid or liquid, uncured or partially cured arylene polysulfide can be mixed with the indicated fillers, and the composition can be cured by applying energy such as heat without causing the melt flow value of arylene polysulfide to a preferred minimum value.

^ Example 1

Powdered phenylene polysulfides known under the trademark Ryton® P3, having a density of 1.3 measured according to ASTM-Dl 505-68 and a melt flow of 75 g / 10 mm, measured according to ASTM, were mixed. D1238-74, (343 ° C and 5 kg load) with varying amounts of clay, talc, calcium carbonate, mica and fiberglass. The percentage by weight of each charge in each of the mixtures is indicated in Table I. The mixture was carried out by tumbling the ingredients of each sample in a rotary drum mixer. Each of the mixtures and a batch of pure phenylene polysulfide of the type used to prepare the mixtures were injection molded into 21.6 cm x 1.3 cm x 3.18 mm bar shaped test tubes suitable for ASTM tensile testing. Each test piece was then tested to determine tensile strength, percent elongation, arc strength (in accordance with ASTM-D495-73). The results are given in Table I.

Table I:

Arc-resistant polyphenylene sulfide

Mixed

D

H

Control 8 Ryton R6 Polyphenylene sulfide

Component (% by weight of the total mixture)

Ryton P3 (phenylene polysulfide) 60

Clay1

Talc2

Calcium carbonate3 Mica4

60

60

60

60

60

60

60

60

45

40

-

-

-

-

20

-

20

17.5

-

40

-

-

-

20

20

-

17.5

-

-

40

-

-

20

20

40

100

Fiberglass 5

-

-

-

-

40

-

-

-

20

Traction (kg / cm2) 7

672

728

562

612.5

1274

721

661.5

542.5

1001

1365

% elongation

1.04

0.8

1.02

0.54

1.08

0.88

1.12

0.83

0.1

1.3

Arc resistance (s) ..

181

178

47

17

24

182

130

133

180

10.8

Izod 9 test (24 ° C).

6

6

6

6

6

Without notch (3.175mm)

2.20

1.93

no no no

2.94

no no

2.2

8.0

test test test

test test

Without notch N.m

2.99

2.63

4.00

2.99

10.88

623,842

Table I (continued)

Arc-resistant polyphenylene sulfide

Mixed

D

G

H

Control 8 Ryton R6 Polyphenylene sulfide

With notch

(3.175mm) 0.27 0.29 0.21 0.36 1.38 0.24 0.25 0.20 0.45 1.4

With notch N.m 0.37 0.39 0.29 0.49 1.88 0.33 0.34 0.27 0.61 1.90

Spiral flow

(cm) 69 56 steps not 43 66 50.8 56

test test

Huber # 200L Desert mineral # 57 Georgia marble # 10 Marietta Suzorite (20-40 mesh) Owens Corning # 497

Some properties are not determined due to low arc resistance; the minimum arc resistance for this resin is 120 s

The minimum desired traction is 73 kg / cm2 (10,000 psi) (69,000 x 103 Pa)

Ryton R6 is the Ryton P3 (powder) in ASTM-D256 pellets

The results show that, by adding the indicated fillers, the tensile strength of the phenylene polysulphide and the percentage of elongation are reduced. However, each of the fillers improved the arc resistance of the polymer. The degree to which arc resistance was improved varied widely with the amount and type of charge. The best arc resistance was obtained with mixtures A, B and I. A much lesser improvement in arc resistance was observed with mixtures G and H. Other mixtures shown in Table I n resulted in a slight improvement in arc resistance, insufficient to meet the minimum arc resistance of 120 s, as measured according to ASTM-D495-73.

It should be noted that the mixture I composed of 17% clay, 17% talc and 20% glass fiber gave a composition having not only a much better arc resistance, but also a tensile strength. less reduced than all the other compositions prepared when a phenylene polysulfide was composed.

Example 2

As long as talc and clay, in combination with a phenylene polysulfide, appeared to have good arc resistance, another series of tests was conducted using various amounts of these two fillers. The tests were carried out by proceeding as indicated in Example 1. The results are shown in Table II.

Table II

Load Arc resistance (s) Flow of the

(% by weight) melt1

Talc Clay (g / mn)

10

10

132

93.6

15

15

183

68.1

20

20

188

37.4

25

25

193

10.7

1 ASTM-Dl 238-74 (343 ° C and 5 kg load).

The data shows that all of the mixtures had an arc resistance above the acceptable value of 120 s, but that the mixtures containing 15% by weight of each charge had much better associated properties of resistance to arc and flow of the melt. Good flow properties of the melt are necessary in order to be able to treat the composition well, in particular by injection molding.

35 Example 3

A mixture of the following ingredients was prepared at the indicated concentrations by mixing the following ingredients in a tumbler:

40 Ingredient Concentration

(% in weight)

Partially cured phenylene polysulfide. 45

Clay 17.5

45 Talc 17.5

Glass 20.0

The mixture was then divided into seven samples. Six of the samples were put into composition with 0.8% by weight of various silanes as follows:

Sample 1 control, no silane

Sample 2 y-glycidoxypropyltrimethoxysilane (Union Carbide) Sample 3 y-glycidoxypropyltrimethoxysilane (Dow) 55 Sample 4 methyltrimethoxysilane (Dow)

Sample 5 polyisoxymethoxysilane (Dow)

Sample 6 methylmethoxysilane (Union Carbide)

Sample 7 long chain alkylsilane (experimental) (Dow)

The samples were injection molded to obtain clear test pieces of a shape suitable for testing. Then the physical and electrical properties and the coefficients of linear thermal expansion of each test piece were tested. The results of the tests are shown in Tables III to V.

( See next page)

65

From the results in Table III, it can be concluded that adding the silanes does not materially affect the physical properties of the samples.

5,623,842

Table III:

Physical properties

Property

Tensile strength1 (psi) (kg / cm2)

Flexural module x 10 "3 2 (psi) (kg / cm2)

Without notch (Izod) 3 (cm-kg / cm)

With notch (Izod) 3 (cm-kg / cm)

Sample

1

(13325) 932.75

(1673.7) 117.16

(2.9) 15.77

(0.55) 2.99

2

(13875) 967.75

(1641.0) 114.87

(2.7) 14.68

(0.53) 2.88

3

(13150) 920.5

(1712.1) 119.85

(2.8) 15.23

(0.57) 3.1

4

(12975) 908.25

(1,733.3) 121.33

(2.4) 13.05

(0.60) 3.26

5

(14475) 1013.25

(1764.1) 123.49

(2.7) 14.68

(0.48) 2.61

6

(14000) 980

(1,723.0) 120.61

(3.0) 16.31

(0.53) 2.88

7

(12200) 854

(1646.2) 115.23

(2.4) 13.05

(0.53) 2.88

1 ASTM-D638-72 2 ASTM-D790-71 3 ASTM-D256-72a

Table IV: Electrical properties

Property Resistance Dielectric constant1 Dielectric constant Volume resistivity2

1.0 kHz 1 MHz arc after 7 days of immersion (2 units)

in water

Immediate

After 7 days

1.0 kHz

1 MHz

immersion

1

195

4.6

4.2

6.1

4.9

3 x 1015

2.8 x 10 12

2

191

4.4

4.2

5.5

4.7

2.4 x 1015

9.7 xlO13

3

193

4.5

4.3

5.6

4.7

1.9 xlO15

1.9 xlO14

4

187

4.5

4.2

5.3

4.6

3.7x10 ”5

7.6 xlO14

5

193

4.4

.4.2

5.0

4.4

4.8x10 ”5

8.4 xlO14

6

193

4.6

4.2

5.4

4.7

2.5 x 1015

2.8 x 1014

7

188

4.4

4.1

5.0

4.5

3.4 xlO15

1.2 x 1015

1 ASTM-Dl 50-70 2ASTM-D257-66

The electrical properties tests in Table IV show that all of the samples had good arc resistance. The dielectric constants of the samples were of the same order of 40

size for all samples but, after 7 days of immersion in water, the dielectric constants of the samples containing the silane were approximately 10 to 20% lower than those of the control sample. The volume resistivity of the control after immersion was 1000 x worse (103), while the samples treated with silane showed relatively little change.

Table V:

Coefficient of linear thermal expansion

Gammede property All values x 106 / ° C

temperature- + 70 ° C + 125 ° C + 140 ° C + 225 ° C tures -30 to + 30 ° C

Sample

1

20.7

21.8

13.4

23.8

42.7

2

20.1

18.2

22.4

21.6

32.3

3

16.8

14.9

17.5

17.5

17.4

4

19.4

erratic

10.7

16.9

39.6

5

17.1

17.1

17.4

17.4

16.9

6

16.9

9.9

15.6

17.8

22.2

7

23.7

19.2

31.3

28.3

58.9

The results indicate that the silanes in samples 3, 5 and 6 cause a significantly lower coefficient of thermal expansion. The silanes, in samples 3 and 5, resulted in the stabilization of the coefficient of linear thermal expansion over the temperature range of the tests.

es In example 7 only, the silane increased the coefficient above that of the control sample (sample 1). The effect on the coefficient of linear expansion was completely unexpected, and this effect is not explained.

R

Claims (12)

623,842 1. Arc-resistant composition, characterized in that it comprises an uncured or partially cured arylene polysulfide and 20 to 50% by weight, relative to the weight of the total composition, of clay and / or talc as a filler. 2. Composition according to claim 1, further containing glass and / or calcium carbonate, the total amount of filler being from 30 to 60% by weight of the total composition. 2 3. Composition according to claim 2, characterized in that the glass content is from 0 to 35% by weight and the calcium carbonate content is from 0 to 40% by weight, relative to the total composition. 4. Composition according to claims 1,2 and 3, characterized in that it further comprises from 0.5 to 5% by weight of at least one silane, relative to the total composition. 5. Composition according to claim 4, characterized in that it comprises from 0.5 to 1% by weight of silane. 6. Composition according to one of claims 4 or 5, characterized in that the silane (s) are chosen from alkylsilanes, alkoxysilanes and their polymers. 7. Composition according to one of claims 4,5 or 6, characterized in that the silane (s) are chosen from the following: γ-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane and polyisoxymethoxysilane. 8. Composition according to one of the preceding claims, characterized in that said arylene polysulfide is a phenylene polysulfide. 9. Composition according to claim 3, characterized in that the phenylene polysulfide constitutes 45% by weight of the total composition and in that the clay, talc and glass respectively constitute 17.5% by weight, 17.5 % by weight and 20% by weight of the total composition. 10. Composition according to one of the preceding claims, characterized in that the arylene polysulfide has an inherent viscosity of at least 0.08 at 206 ° C, measured as described above. 11. Composition according to claim 10, characterized in that the inherent viscosity is from 0.1 to 0.3. 12. Use of a composition according to claim 1 for the manufacture of molded articles for electrical appliances, characterized in that the composition is subjected to an injection molding or a pressure molding.