Process for vulcanizing rubber at a low temperature

Abstract

A process for vulcanizing a rubber base comprising at least one halogen-containing amorphous polymer at a low temperature ranging from 5.degree. to 85.degree. C., which comprises carrying out the vulcanization in the presence of 0.01 to 20 parts by weight of an organic hydroperoxide and/or ketone peroxide per 100 parts by weight of the rubber base.In the above process, at least one member selected from the group consisting of (I) the oxides of metals, such as zinc, lead, chromium, cobalt, nickel, magnesium, manganese, copper and iron, or the metallic salts of said metals with aliphatic or cycloaliphatic carboxylic acid having 8 to 24 carbon atoms; (II) methacrylic esters; (III) maleimides; and (IV) oximes, may be used as a vulcanization activator or a vulcanization accelerator in an amount of 0.01 to 20 parts by weight per 100 parts by weight of the rubber base.

Description

The present invention relates to a process for vulcanizing at least one halogen-containing amorphous polymer at a low temperature. More particularly, it pertains to a process for vulcanizing at least one halogen-containing amorphous polymer at a low temperature, in which an organic hydroperoxide and/or ketone peroxide as a vulcanizing agent is used alone or in combination with a specific vulcanization activator or accelerator to achieve the vulcanization at a temperature as low as from 5.degree. to 85.degree. C.

As the known literature references concerning a low temperature vulcanization process using an organic hydroperoxide as a vulcanizing agent, there are Japanese Pat. Nos. 19,930/67 and 16,584/70. These relate to amorphous copolymers consisting of ethylene, alpha-olefin and cyclic or acyclic polyene having nonconjugated double bond. There is found no literature concerning the halogen-containing amorphous polymers which are the object of the present invention.

At present, halogen-containing amorphous polymers are, in many cases, used in adhesives, paints and sealants. It is greatly significant that a low temperature vulcanization be applicable to these uses. In order to attain this object, therefore, the present inventors have long done extensive research on the low temperature vulcanization of halogen-containing amorphous polymers to achieve this invention. This invention is characterized by using an organic hydroperoxide or ketone peroxide as a vulcanizing agent.

An object of the present invention is to provide a process for vulcanizing halogen-containing amorphous polymers at a low temperature.

Another object of the present invention is to provide a process for vulcanizing at a low temperature halogen-containing amorphous polymers, which process is applicable to adhesives, paints and sealants.

A further object of the present invention is to provide a process for vulcanizing halogen-containing amorphous polymers at a low temperature, in which an organic hydroperoxide or ketone peroxide is used as a vulcanizing agent.

A still further object of the present invention is to provide a process for vulcanizing halogen-containing amorphous polymers at a low temperature, in which an organic hydroperoxide or ketone peroxide as a vulcanizing agent is used together with a vulcanization activator or a vulcanization accelerator.

The other objects and advantages of the present invention will become clear from the following description.

According to the present invention, there is provided a process for vulcanizing a rubber base comprising at least one amorphous polymer at a low temperature ranging from 5.degree. to 85.degree. C., which comprises carrying out the vulcanization in the presence of 0.01 to 20 parts by weight of an organic hydroperoxide and/or ketone peroxide per 100 parts by weight of the rubber base, and, if necessary, in the presence of 0.01 to 20 parts by weight of at least one vulcanization activator or accelerator selected from the group consisting of (I) metal oxides or metallic salts of aliphatic or cycloaliphatic carboxylic acids having 8 to 24 carbon atoms, (II) methacrylates, (III) malcimides and (IV) oximes, per 100 parts by weight of the rubber base.

The halogen-containing amorphous polymers in the present invention include, for example, chloroprene rubber, chlorinated polyethylene, chlorosulfonated polyethylene and chlorinated ethylene-propylene-diene rubber, and the halogens include chlorine and bromine. Chlorine is the most popular and important.

The rubber base in the present invention includes halogen-containing amorphous polymers alone, mixtures thereof and mixtures of halogen-containing amorphous polymer and halogen-free amorphous polymers. More particularly, it includes not only a mixture obtained by mixing the halogen-containing amorphous polymer with the halogen-free amorphous polymer for the purpose of enhancing the weather resistance and heat resistance and reducing the cost of the halogen-containing amorphous polymer but also a mixture obtained by mixing the halogen-free amorphous polymers with the halogen-containing amorphous polymer for the purpose of enhancing the tackiness and adhesiveness of the halogen-free amorphous polymer or imparting flame-proof property to the halogen-free amorphous polymer. In other words, it is indispensable for the rubber base described herein to comprise at least one halogen-containing amorphous polymer. The halogen-free amorphous polymers include, for example, styrene-butadiene rubber, ethylene-propylene-diene rubber and natural rubber. Further, the halogen-free amorphous polymers used for the present invention include low molecular weight amorphous copolymers such as low molecular weight ethylene-propylene rubber, too.

The organic hydroperoxides and ketone peroxides used in the present invention include, for example, alpha-cumyl hydroperoxide, tertiary butyl hydroperoxide, p-menthane hydroperoxide, m,p-diisopropylbenzene-monohydroperoxide, methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, acetylacetone peroxide, and the like.

Another great feature of the present invention is that at least one compound belonging to the following groups may be used as a vulcanization activator or a vulcanization accelerator to adjust the vulcanization velocity:

(I) The oxides of metals such as zinc, lead, chromium, cobalt, nickel, magnesium, manganese, copper and iron; and the metallic salts of these metals with aliphatic or cycloaliphatic carboxylic acids having 8 to 24 carbon atoms.

The aliphatic or cycloaliphatic carboxylic acid having 8 to 24 carbon atoms mentioned in group (I) include, for example, n-octoic acid, naphthenic acid, abietic acid, lignoceric acid and 2-ethylhexanoic acid.

(II) Methacrylic esters such as ethylene dimethacrylate, 1,3-butylene dimethacrylate, triethylolpropane trimethacrylate, and the like.

(III) Maleimides such as N,N'-m-phenylene bismaleimide, phenyl maleimide, and the like.

(IV) Oximes such as p-quinone dioxime, p,p'-dibenzoyl quinone dioxime, and the like.

In the present invention the vulcanizing agent is used in an amount of 0.01 to 20 parts by weight, preferably 0.5 to 15 parts by weight per 100 parts by weight of the rubber base. The vulcanization activator or the vulcanization accelerator is used in an amount of 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight per 100 parts by weight of the rubber base. The respective quantities of the vulcanizing agent and the vulcanization activator or the vulcanization accelerator are decided depending upon the application and the object. In general, the vulcanization velocity is somewhat accelerated with an increase in amount of these compounding agents. Further, when the vulcanizing agent and the vulcanization activator or accelerator are liquid, they can be applied as they are, or when they are solid, in the form of solutions in proper organic solvents, to the surface of an objective to be vulcanized by spraying or brushing. Accordingly, it is not always necessary to use them in admixture with the rubber base, fillers or other compounding agents.

The rubber base usable for the present invention may contain various fillers such as carbon black, talc, calcium carbonate, etc.; various higher fatty acids; coloring agents; anti-oxidants; ultraviolet absorbers; and softening agents including mineral oils.

By using the process of the present invention, there can be produced various rubber products, sheets, roofings, sealants, adhesives, paints, and the like.

Referring to Examples, the present invention is further illustrated, but should not be interpreted to be limited thereto.

EXAMPLE 1

Using chloroprene rubber as the halogen-containing amorphous polymer, examination was made on the representative vulcanization system with or without vulcanization activator or accelerator. The result thereof is shown below.

Composition

______________________________________Chloroprene rubber(Raw rubber Mooneyviscosity, ML.sub.1+4 = 47(100.degree. C.); 100 parts by weightdensity = 1.23)SRF carbon black 50 parts by weightZinc oxide 5 parts by weightStearic acid 1 parts by weightNaphthenic oil 10 parts by weightAlpha-cumyl hydroper-oxide (Concentration: 7 parts by weight70% by weight)Vulcanization accelerator 2 parts by weight______________________________________

Test Method

The above-mentioned materials were blended in a mixing roll and formed into a sheet with a thickness of 1 mm, which was then allowed to stand at 40.degree. C. After a given time, the sheet was subjected to measurement of tensile strength and elongation according to JIS K-6301 (JIS is an abbreviation of Japan Industrial Standards) to examine the vulcanization state. The result obtained is as shown in Table 1.

Table 1______________________________________ Vulcanization Accelerator p-Quinone Ethylene -- dioxime dimethacrylate CharacteristicsVulcanization T.sub.B E.sub.B T.sub.B E.sub.B T.sub.B E.sub.Btime (day) (kg/cm.sup.2) (%) (kg/cm.sup.2) (%) (kg/cm.sup.2) (%)______________________________________1 27 930 18 1120 50 7303 37 700 46 910 68 4506 36 710 71 710 77 330______________________________________ Note: T.sub.B : Tensile strength at break E.sub.B : Elongation at break

EXAMPLE 2

Examination was made on a chlorinated ethylene-propylene-diene rubber as the halogen-containing amorphous polymer. The result thereof is shown below.

Composition

______________________________________Chlorinated ethylene-propylene-diene rubber 100 parts by weightHAF carbon black 50 "Zinc oxide 5 "Stearic acid 1 "Naphthenic oil 10 "Alpha-cumyl hydroper-oxide (Concentration: 7 "70% by weight)Vulcanization accelerator 2 "______________________________________ The above chlorinated ethylene-propylene-diene rubber was obtained by chlorinating an ethylene-propylene-5-ethylidene-2-norbornene rubber having a raw rubber Mooney viscosity of ML.sub.1+4 =40(100.degree. C.), an iodine value of 12 and a propylene content of 50% by weight, to a chlorine content of 25% by weight.

Test Method

The same test method as in Example 1 was repeated. The result obtained is shown in Table 2.

Table 2______________________________________Vulcanization p-Quinoneaccelerator -- dioxime T.sub.B E.sub.B T.sub.B E.sub.BCharacteristics (Kg/cm.sup.2) (%) (Kg/cm.sup.2) (%)______________________________________Vulcanization 1 12 570 12 570time (day) 5 18 820 24 640 10 30 870 45 650 20 65 730 135 470 30 103 570 165 430______________________________________

EXAMPLE 3

Using chloroprene rubber, examination was made on metal oxides and metal salts of higher fatty acids as the vulcanization accelerator or activator. The result obtained is shown below.

Composition

The same as in Example 1, except that the amounts of vulcanizaton accelerator added are as shown in Table 3.

Test Method

The same as in Example 1. The result obtained is shown in Table 3.

Table 3__________________________________________________________________________ Chro- * Cobalt* Iron* mium Cobalt* Magne- Lead Magne-(*)Vulcanization naphth- naph- naph- abie- sium mono- Cobalt*(*) siumaccelerator enate thenate thenate tate oxide oxide abietate oxideAmount (phr) 1 1 1 1 10 10 10 10__________________________________________________________________________Characte- Vulca-ristics niza- tion time (day) 1 27 105 57 44 82 44 32 9 15T.sub.B 3 37 118 72 46 103 81 47 7 21(kg/cm.sup.2) 5 36 100 72 50 101 91 46 8 19 12 38 102 76 54 110 98 61 11 20E.sub.3 1 930 590 860 880 780 780 850 1110 690(%) 3 700 420 630 630 560 580 610 1150 690 5 700 380 590 600 500 490 580 1000 620 12 550 340 390 490 400 420 490 1150 680__________________________________________________________________________ *Metal content: 5% by weight (*)Referential Example: alpha-cumyl hydroperoxide was not mixed.

Example 3 fully proves the necessity of alpha-cumyl hydroperoxide as the vulcanizing agent and the effect of the oxides of these metals or the salts of these metals with higher fatty acids as the vulcanization accelerator or activator.

EXAMPLE 4

Examination was made on the effect of a vulcanization accelerator upon chloroprene at 40.degree. C. and 70.degree. C. The result thereof is shown below.

Test Method

The same as in Example 1. The result obtained is shown in Table 4.

Table 4__________________________________________________________________________ Ethylene N,N'-m-Vulcanization -- p-Quinone dimetha- phenylene Cobaltaccelerator dioxime crylate bismaleimide abietate__________________________________________________________________________ Chloroprene rubber (Raw Rubber Mooney 100 100 100 100 100 visusity, ML.sub.1+4 = 47 (100.degree. C.); Density = 1.23)Composition) SRF carbon black 50 50 50 50 50(part by weight) Naphthenic oil 10 10 10 10 10 Zinc oxide 5 5 5 5 5 Stearic acid 1 1 1 1 1 Alpha-cumyl 7 7 7 7 7 hydroperoxide Vulcanizaton accelerator 0 2 2 2 1__________________________________________________________________________Vulcanizationtemperature (.degree. C.) 40 70 40 70 40 70 40 70 40 70__________________________________________________________________________ Vulcan- 1 38 105 50 111 66 102 76 118 77 123T.sub.B 3 53 114 59 134 58 110 94 130 106 128 zation 6 55 102 56 141 55 108 98 144 102 119(kg/cm.sup.2) 9 56 106 61 136 61 -- 87 128 110 -- time (day) 15 58 -- 69 -- 65 -- 94 -- 108 -- Vulcani- 1 890 380 870 320 520 270 560 160 600 300E.sub.B 3 740 280 880 280 470 310 390 160 450 310 zation 6 650 230 850 240 440 210 230 140 430 250(%) 9 680 220 810 240 400 -- 290 130 360 -- time (day) 15 600 -- 710 -- 380 -- 240 -- 350 --__________________________________________________________________________

EXAMPLE 5

Examination was made on the effect of carbon black upon the low temperature vulcanization of the same chlorinated ethylene-propylene-diene rubber as in Example 2. The result thereof is given below.

Composition

______________________________________Chlorinated ethylene-propylene-diene rubber 100 parts by weightCarbon black 50 "Naphthenic oil 5 "Zinc oxide 5 "Stearic acid 1 "Alpha-cumylhydroperoxide 7 "p-Quinome dioxime 2 "______________________________________

Test Method

The same as in Example 1. The result obtained is shown in Table 5.

Table 5______________________________________Kind of carbon black ISAF HAF FEF GIF______________________________________ 1 13 9 11 8T.sub.B Vulcani- 6 15 14 13 11(kg/cm.sup.2) zation 20 123 111 102 68 time (day) 30 202 149 133 105 Vulcani- 1 370 350 390 450E.sub.B zation 6 620 650 790 760(%) time 20 480 470 520 590 (day) 30 330 350 400 450______________________________________

EXAMPLE 6

Examination was made on mixtures of a halogen-containing amorphous polymer and the halogen-free amorphous copolymer as the rubber base, in which chloroprene rubber was used as the halogen-containing amorphous polymer and the same ethylene-propylene-diene rubber as in Example 2 was used as the halogen-free amorphous copolymer.

Test Method

The same as in Example 1. The result obtained is shown in Table 6.

Table 6__________________________________________________________________________ Chloroprene rubber(Raw rubber Mooney viscosity, 100 75 50 25 --* ML.sub.1+4 = 47 (100.degree. C.); density = 1.23)Composition Ethylene-propylene-diene rubber -- 25 50 75 100(part by SRF carbon black 50 50 50 50 50weight) Naphthenic oil 10 10 10 10 10 Zinc oxide 5 5 5 5 5 Stearic acid 1 1 1 1 1 Alpha-cumyl hydroperoxide 7 7 7 7 7 Cobalt abietate 0.5 0.5 0.5 0.5 0.5 p-Quinone dioxime 2 2 2 2 2 1 60 47 41 54 81T.sub.B Vulcanization 3 73 64 68 69 101(kg/cm.sup.2) time (day) 10 87 88 93 80 102 1 780 660 510 420 340E.sub.B Vulcanization 3 530 490 490 420 350(%) time (day) 10 400 420 420 340 300__________________________________________________________________________ *Referential example

EXAMPLE 7

Examination was made on the effect of vulcanizing agent upon the low temperature vulcanization of chloroprene rubber as the halogen-containing amorphous polymer.

Composition

______________________________________Chloroprene rubber(Raw rubber Mooney viscosity, 100 parts by weightML.sub.1-4 = 47 (100.degree. );density = 1.23)SRF carbon black 50 "Naphthenic oil 10 "Zinc oxide 5 "Stearic acid 1 "Cobalt abietate 0.5 "Vulcanizing agent 1/30 mole.______________________________________

Test Method

The same test method as in Example 1 was repeated, except that vulcanization was carried out at room temperature.

The result obtained is shown in Table 7.

Table 7__________________________________________________________________________ m.p-Diiso- Tertiary- propyl p-Menthane Methyl ethylKind of vulca- butyl benzene mono- hydro- ketenenizing agent hydrooperoxide hydroperoxide peroxide peroxide__________________________________________________________________________ 1 35 69 61 26T.sub.B Vulcaniza- 3 45 93 82 35(kg/cm.sup.2) tion time 5 53 89 85 45 (day) 7 72 101 89 48 10 69 105 94 58 1 830 750 780 810E.sub.B Vulcani- 3 790 700 750 790(%) zation time 5 690 690 740 770 (day) 7 610 600 700 730 10 610 500 690 690__________________________________________________________________________

Claims

1. A process for vulcanizing a non-aqueous chloroprene rubber base comprising chloroprene rubber at a low temperature consisting essentially of

vulcanizing said non-aqueous chloroprene rubber base at a temperature ranging from 5.degree. to 85.degree. C. in the presence of

0.01 to 20 parts by weight of at least one vulcanizing agent selected from the group consisting of an organic hydroperoxide and ketone peroxide per 100 parts by weight of said chloroprene rubber, and

0. 01 to 20 parts by weight of at least one vulcanization activator or accelerator selected from the group consisting of oxides of zinc, lead, chromium, cobalt, nickel, magnesium, manganese, copper, and iron per 100 parts by weight of said chloroprene rubber.

2. A process as defined in claim 1, wherein the amount of the vulcanizing agent is in a range of 0.5 to 15 parts by weight.

3. A process as defined in claim 1, wherein the vulcanizing agent is selected from the group consisting of alpha-cumyl hydroperoxide, tertiary-butyl hydroperoxide, p-menthane hydroperoxide, m,p-diisopropylbenzene monohydroperoxide, methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide and acetylacetone peroxide.

4. A process as defined in claim 1, wherein the vulcanizing agent is alpha-cumyl hydroperoxide.

5. The process of claim 1 wherein said vulcanization activator or accelerator is zinc oxide.