Polychloroprene compositions

Abstract

Essentially ETU-free cross linkable compositions comprising chloroprene rubber, a cross-linker and a vulcanization accelerator, which have a defined content of ions from the second or third main group and resinate anions and thus possesses improved curing characteristics, a process for vulcanization of such compositions and vulcanizates obtained thereby.

Claims

1. A cross-linkable composition comprising: a chloroprene rubber comprising: cations of metals from the second or third main group in an amount of more than 0.25% by weight based on the total amount of chloroprene rubber; resinate anions in an amount of more than 2.5% by weight and less than 4.5% by weight based on the total amount of chloroprene rubber; a cross-linker, and a vulcanization accelerator selected from N-methyl-thiazolidine-2-thione derivatives.

2. The cross-linkable composition according to claim 1, wherein the cations of metals from the second or third main group are selected from calcium, magnesium, aluminium or a combination thereof.

3. The cross-linkable composition according to claim 1, wherein the amount of cations of metals from the second or third main group is more than 0.25% by weight to 0.40% by weight.

4. The cross-linkable composition according to claim 1, wherein the amount of resinate anions is more than 2.7% by weight.

5. The cross-linkable composition according to claim 1, wherein the cross-linker is a metal oxide.

6. The cross-linkable composition according to claim 1, wherein the chloroprene rubber is obtained by a process comprising: adjusting the pH of a polychloroprene latex to a value above 10.5 and not more than 13.5; and coagulating the pH-adjusted latex by addition of a salt of a metal of the second or third main group being a calcium and/or magnesium salt.

7. A process for the production of vulcanisates, the process comprising heating a cross linkable composition according to claim 1 to a temperature 100 C. to 200 C.

8. A vulcanizate obtainable by the process according to claim 7.

9. A molded article of manufacture comprising the vulcanizate according to claim 8.

10. A chloroprene rubber comprising cations of metals from the second or third main group, in an amount of more than 2.5% by weight and less than 4.5% by weight based on the total amount of chloroprene rubber.

11. The chloroprene rubber according to claim 10, wherein the cations of metals comprise calcium, magnesium, aluminum or a combination thereof, the amount of cations is greater than 0.25% by weight to 0.40% by weight, and the amount of resinate anions is more than 2.7% by weight.

12. The chloroprene rubber according to claim 11, wherein the amount of cations is greater than 0.26% by weight to 0.35% by weight, and the amount of resinate anions is between 2.9% by weight and 3.7% by weight.

13. The cross-linkable composition according to claim 1, wherein: the cations of metals from the second or third main group are selected from the group consisting of calcium, magnesium, aluminium or a combination thereof; the amount of cations of metals from the second or third main group is 0.26% by weight to 0.35% by weight; the resinate anions are anions of abietic acid, dehydroabietic acid, dihydroabietic acid, neoabietic acid, palustric acid, levopimaric acid, pimaric acid or isopimaric acid, as well as their isomers, hydrogenated forms and dehydrogenated forms; and the amount of resinate anions is more than 2.7% by weight.

14. The cross-linkable composition according to claim 13, wherein: resinate anions are anions of abietic acid, dehydroabietic acid and dihydroabietic acids; the cross-linker is a metal oxide selected from zinc oxide and magnesium ocide and mixtures thereof; the vulcanization accelerator is selected from N-methyl-thiazolidine-2-thione, N-methyl-thiazolidine-2-thione, hexamethylene tetramine and triazine derivatives; and the chloroprene rubber is obtained by a process comprising: adjusting the pH of a polychloroprene latex to a value between 11.0 to 13.2; and coagulating the pH adjusted latex by addition of a calcium and/or magnesium salt.

15. The cross-linkable composition according to claim 6, wherein the chloroprene rubber is obtained by a process comprising adjusting the pH of the polychloroprene latex to a value between 11.0 to 13.2 prior to said coagulating.

16. The process according to claim 7, wherein said temperature is from 140 C. to 180 C.

Description

EXAMPLES

(1) The chloroprene latices used for the following examples were obtained by the following polymerization recipe (batch experiments, quantities given in parts by weight):

(2) TABLE-US-00001 Chloroprene and 2,3-dichlorobutadiene 100 Desalinated water 125 Resin acid 3 Na-Salt of condensation product consisting 0.5 of naphthalene sulfonic acid and formaldehyde n-Dodecylmercaptan (n-DDM) 0.2 KOH 0.5

(3) The polymers obtained from 100 parts by weight technical grade chloroprene were referred to as homopolymers, whereas the polymers obtained from a monomer mixture comprising 93 parts by weight technical grade chloroprene and 7 parts by weight technical grade 2,3-dichlorobutadiene were referred to as copolymers.

(4) The technical grade chloroprene may also contain 1-chlorobutadiene, typically in an amount from 0% to 2% by weight.

(5) The polymerization was carried out in a 4 L flask. The aqueous phase made of desalinated water, resin acid, KOH and a Na-Salt of the condensation product of naphthalene sulfonic acid and formaldehyde was placed in this vessel, flushed with nitrogen and heated to a temperature of 45 C. The monomers were added when the medium temperature reached 40 C. Subsequently, the emulsion temperature was stabilized at 45 C. before starting the polymerization. The polymerization was started by constantly adding a solution of thiourea dioxide in water (3% by weight) at flow rate between 0.1 ml/min and 5 ml/min, the latter being adjusted to achieve 70% monomer conversion within 180 min. The conversion rate was determined by gravimetric analysis. The polymerization was stopped with a 0.03% parts by weight, based on the latex, of an aqueous 2.5% by weight solution of diethyl hydroxylamine when the monomer conversion reached 70%. The latex was degassed to a residual chloroprene content below 1000 ppm (based on the latex).

(6) For Reference Examples 1 and 2, the degassed latex pH was adjusted to 7.5 with a 20% by weight aqueous acetic acid solution. The polymer was isolated by freezing coagulation and washed with salt-free water. The sheets obtained were dried to a residual moisture content below 0.6% by weight in a circulating air drying cupboard at 70 C.

(7) For Reference Example 3 the degassed latex was diluted with water to 15% solid content and its pH adjusted to a value of 9 with a 20% aqueous acetic acid. The latex was precipitated with 0.25% calcium chloride in water at room temperature. The coagulate was washed with salt-free water and dried to a residual moisture content below 0.6% by weight in a circulating air drying cupboard at 70 C.

(8) For Examples 1 to 4 according to the invention, the degassed latex was diluted with water to 15% solid content and its pH adjusted to a value between 13 and 11 with a 20% aqueous acetic acid. The latex was precipitated with 0.25% calcium chloride in water at room temperature. The coagulate was washed with salt-free water and dried to a residual moisture content below 0.6% by weight in a circulating air drying cupboard at 70 C.

(9) All rubber compounds were based on the following recipe:

(10) TABLE-US-00002 No. Component phr 1 Chloroprene rubber (homo- or copolymer) 100 2 Carbon Black N772 30 3 Stearic acid 0.5 4 Maglite DE 4.1 5 Rhenogran MTT-80 0.5 6 Zinc Oxide read seal 5 .sup.1 phr: parts per hundred rubber

(11) They were processed in a 1.5 l intermeshing internal mixer according to the following sequence:

(12) TABLE-US-00003 Absolute time [min] Rotation speed [RPM] Components added (No.) 0 44 1 4 44 2, 3, 4 6 44 5, 6 7 end

(13) Methods

(14) The latex pH was measured with a Schott H 63 glass electrode (Electrolyte: KCl 3 mol/l, Silamid reference system) at 20 C.

(15) In the absence of disturbing substances (e.g. additives) the resinate anion content could be determined by titration of a 2.2% by weight polymer solution in tetrahydrofuran with a 0.1M perchloric acid solution. The titration was monitored by potentiometry (Metrohm Solovotrode Nr 6.0229.100), the volume of perchloric acid added to reach the first potential step (V.sub.equivalent) was used to calculate the salt amount in the polymer:

(16) $\mathrm{resinate}\mathrm{anion}\left[\%\right]=\frac{V_{\mathrm{equivalent}}300.5}{{\mathrm{mass}}_{\mathrm{polymer}\mathrm{solution}}2.2}$

(17) Where:

(18) V.sub.equivalent is expressed in milliliters

(19) Mass.sub.polymer solution is expressed in grams

(20) The resulting value is the salt content expressed as a percentage value.

(21) For the ion concentration determination, about 0.2 g rubber sample was digested with mineral acid (5 mL HNO.sub.3 (63%), 3 mL H2O) in a microwave oven (Mikrowelle Ultraclave III) according to the following temperature program: 8 min 70 C. 100 bar 700 Watt 20 min 140 C. 120 bar 700 Watt 10 min 210 C. 160 bar 1000 Watt 12 min 250 C. 160 bar 1000 Watt 18 min 280 C. 160 bar 1000 Watt

(22) The prepared sample was then analyzed by ICP-OES (Varian Vista Pro, wavelength 216.956 nm, 407.771 nm and 421.552 nm (reported value is the mean value), 1.2 kW plasma power, 15 l/min plasma gas, 10 s measurement time repeated 3 times, calibration with external standards. In ICP-OES analysis, atoms were excited by inductively coupled plasma. The emitted light of specific wavelength was detected and corresponded to their concentration (in % by weight) in the sample.

(23) The Mooney scorch at 120 C. is determined according to DIN 53 523 Part 4 and MS-t5 as defined in paragraph 2.2 (MS-t5 is the time from the beginning of the measurement up to the point at which the Mooney viscosity increased by 5 Mooney units above the viscosity minimum).

(24) The vulcanization behavior of the compositions was determined in a Monsanto rheometer MDR 2000E at 160 C. and 180 C. in accordance with DIN 53 529. The characteristic vulcanization times tS1, t10 and t90, as well as S were determined in this way.

(25) In accordance with DIN 53 529, part 3: t10: time at which 10% of the conversion has been achieved t90: time at which 90% of the conversion has been achieved S: difference between the maximum and the minimum torque

(26) The Shore A hardness (H), tensile strength (TS) and the elongation at break (EB) of the vulcanizates were determined by means of a tensile test in accordance with DIN EN ISO 868 and DIN 53504, respectively.

Examples

(27) TABLE-US-00004 resinate Scorch MDR 45 min@160 C. MDR 45 min@180 C. Mechanical Properties pH anion Ca.sup.2+ MS t5 S t10 t90 t90 t10 t10 t90 t90 t10 H TS EB Sample Composition Latex % % min dNm min min min min min min Sh A MPa % Ref 1 Copolymer 7.5 1.07 <0.01 32.1 10.1 2.9 40 37.3 1.8 34.7 32.9 62 19 349 Ref 2 Homopolymer 7.5 1.07 <0.01 26.7 12 3.4 39.9 36.5 2.7 28.7 26 63 20.0 348 Ref 3 Copolymer 9.0 1.84 0.21 45.0 16.5 7.0 29.2 22.2 2.6 20.2 17.6 62 17.9 323 Ref4 Homopolymer 7.5 1.33 0 20.6 15.6 5.3 40 34.7 2.7 20.6 17.9 Ref 5 Homopolymer 7.5 4.89 0.24 15.6 11.5 3 39 35.7 1.7 30.7 29.0 Example 1 Copolymer 12.8 3.02 0.26 47.9 14.4 8.1 37.3 29.2 3.1 14.8 11.7 60 21.5 374 Example 2 Copolymer 11.0 2.99 0.30 48.4 15.7 7.7 32.4 24.7 2.8 15.5 12.7 62 19.6 341 Example 3 Homopolymer 13.1 3.51 0.29 >50 14.3 9.4 39.6 30.2 3.5 15.3 11.8 61 21.3 371 Example 4 Homopolymer 11.0 3.21 0.27 49.1 16.1 8.2 34.9 26.7 2.9 14.4 11.5 62 19.6 343

(28) Reference Example 4 was obtained according to the method disclosed in U.S. Pat. No. 2,567,117 A and Reference Example 5 was obtained by addition of 4 phr calcium resinate to the polymer of Example 4 in analogy to Example 5 of U.S. Pat. No. 3,310,546 A (although 5 phr of calcium resinate were used in the latter). The results in the table show that when the resinate anions content and the content of cations from the second or third main group is in the range according to the invention, the processing safety (MS t5) is improved significantly and at the same time, the effective vulcanization time (t90-t10) and the vulcanization time (t90) at 180 C. are improved (decreased) as well.