EP1311636A2

EP1311636A2 - Rubber blends containing isocyanatosilane and microgel

Info

Publication number: EP1311636A2
Application number: EP01958017A
Authority: EP
Inventors: Werner Obrecht; Martin Mezger; Anthony Sumner
Original assignee: Bayer AG
Current assignee: Lanxess Deutschland GmbH
Priority date: 2000-08-08
Filing date: 2001-07-25
Publication date: 2003-05-21
Also published as: KR20030024845A; MXPA03001185A; AU2001279783A1; WO2002012389A3; BR0113047A; DE10038488A1; US6632888B2; US20020049282A1; WO2002012389A2; KR100684251B1; TW574293B; CA2418354A1; JP2004506058A

Abstract

The invention relates to rubber blends, which contain microgels and isocyanatosilanes, and to vulcanizates produced therefrom. By adding the isocyanatosilanes, the mechanical properties of the vulcanizates, especially the expansion properties and wear resistance, are improved without reducing the difference of the rebound elasticities at 70 DEG C and 23 DEG C.

Description

Rubber mixtures containing isocyanatosilane and microgel

The invention relates to rubber mixtures which contain microgels and isocyanatosilanes and to vulcanizates produced therefrom. The addition of the isocyanatosilanes improves the mechanical properties of the vulcanizates, in particular the stretching properties and the abrasion resistance, without reducing the difference between the rebound elasticities at 70 ° C. and 23 ° C.

The use of crosslinked rubber particles in rubber compounds is among others described in the following patents and patent applications: US-A 5 124 408 (sulfur-modified CR gels), US-A 5 395 891 (BR gels), DE-A 19 726 729 (SBR gels) and DE patent application 19 701 487.9 (NBR gels). In these publications, the complete or partial substitution of carbon black or other inorganic fillers such as silica by polymeric fillers on the

Basis of rubber gels described. The vulcanizates produced therefrom are particularly suitable for the production of rubber articles and tire components such as tire treads. Vulcanizates with rubber gels in particular, based on CR, SBR and NBR microgels, have high rebound resilience at 70 ° C and thus low rolling resistance, and low rebound resilience at 23 ° C and thus high wet slip resistance. The difference in rebound elasticities between 70 ° C and 23 ° C is characteristic of rubber compounds that contain these microgels. However, the mechanical properties of the microgel-containing vulcanizates are not sufficient for use in technical rubber articles and in tire components. Deficits exist particularly in the level of mechanical vulcanizate properties. There is therefore a need to improve the stress value at 300% elongation and elongation at break as well as the abrasion resistance.

The production and use of sulfur-containing organosilicon compounds is described, inter alia, in the following patent publications: DE-A 2 141 159, US-A 3,873,489, US-A 5,110,969, US-A 4,709,065 and US-A 5,227,425. These publications describe the positive influence of sulfur-containing organosilicon compounds on the mechanical properties of vulcanizates filled with silica. However, the use of sulfur-containing organosilicon compounds in combination with mixtures containing rubber particles is not taught, nor is the use of sulfur-free organosilanes in combination with rubber mixtures taught. The use of isocyanatosilanes to improve the mechanical properties of rubber compounds which contain crosslinked rubber particles is also not taught.

In addition, the use of diisocyanates for vulcanization with natural rubber is described in O. Bayer, Angewandte Chemie, Edition A, 59th year, No. 9, pp. 257-288, September 1947. The mechanical properties of the vulcanizates obtained are, however, unsatisfactory , In addition, the vulcanizate adhered very strongly to the metal parts of the vulcanizing molds. The use of isocyanatosilanes for the vulcanization of rubber compounds that contain rubber gels as fillers is not taught by O. Bayer.

The task was therefore to determine the mechanical value level (product of the stress value at 300% elongation and elongation at break) and the abrasion resistance

(DIN abrasion) to improve rubber vulcanizates containing microgel without worsening the difference in rebound elasticities at 70 ° C and 23 ° C.

It has now been found that the addition of isocyanatosilanes to microgel-containing rubber mixtures achieves the aforementioned goals.

The invention therefore relates to rubber mixtures containing at least one double bond-containing rubber (A), at least one microgel (B) and at least one isocyanatosilane (C), the proportion of double bond-containing rubber (A) being 100 parts by weight and the proportion of rubber gel (B ) 1 to 150% by weight

Parts, preferably 10 to 20 parts by weight, and the proportion of isocyanatosilane (C) 0.2 to 20 parts by weight, preferably 1 to 10 parts by weight, and further rubber auxiliaries and fillers.

Double-bonded rubber (A) means the rubbers which are referred to as R rubbers according to DLN / ISO 1629. These rubbers have a double bond in the main chain. These include, for example:

NR: natural rubber

SBR: styrene / butadiene rubber BR: polybutadiene rubber

NBR: nitrile rubber

IIR: butyl rubber

HNBR: hydrogenated nitrile rubber

SNBR: styrene / butadiene / acrylonitrile rubber CR: polychloroprene

XSBR: carboxylated styrene / butadiene rubber

XNBR: carboxylated butadiene / acrylonitrile rubber

ENR: epoxidized natural rubber

ESBR: epoxidized styrene / butadiene rubber

However, rubbers containing double bonds are also to be understood to mean rubbers which are M rubbers in accordance with DIN / ISO 1629 and in addition to the saturated rubbers

Main chain have double bonds in side chains. This includes e.g. EPDM.

The following are preferred: NR, BR, SBR, SNBR, IIR and EPDM.

Crosslinked rubber particles (B), also referred to as rubber gels or microgels, are described, for example, in US Pat. No. 5,124,408, US Pat. No. 5,395,891, DE-A

19 726 729 and in DE patent application 19 701 487.9. Rubber rubbers with functional groups with acidic hydrogen which are mixed with alkoxysilane are preferred. NEN or reacts with isocyanates. Preferred functional groups are hydroxyl groups, carboxyl groups, amino groups or amido groups.

Particularly suitable as rubber gels are: BR, NR, NBR, CR and / or SBR gels which are optionally equipped with groups on the surface of the gels and which are able to react with the isocyanatosilanes. Such groups are, for example, the functional groups mentioned above.

A rubber gel which is hydroxyl-modified can be used particularly advantageously, the acrylates and methacrylates of

Hydroxyethanol, hydroxypropanol and hydroxybutanol can be used. The amount of hydroxylating agent is 0.1 to 50 phr based on the unmodified rubber gel. 0.5 to 20 phr are particularly preferred. Hydroxybutyl acrylate is particularly preferably used in amounts of 0.5 to 20 phr for the hydroxyl modification.

The microgels have particle diameters of 5-1000 n, preferably 20-600 nm (D VN value according to DIN 53206). The diameter specifications d_o, d ₅₀ and d ₈₀ denote characteristic diameters in which 10, 50 and 80 parts by weight of the sample each have a diameter which is smaller than the corresponding characteristic diameter.

The particle diameter is determined by means of ultracentrifugation.

Because of their crosslinking, the rubber gels are insoluble and suitable

Swelling agents such as toluene swellable. The gel content of the rubber gels is> 80% by weight.

The swelling indices of the microgels (QI) in toluene are 1-50, preferably 1-20. The gel content and swelling index (QI) of the rubber gels are determined by extracting the sample with toluene at room temperature. The gel content indicates the percentage by weight of the portion which sediments and can be separated off in toluene when centrifuged at 20,000 rpm.

The swelling index is calculated from the weight of the solvent-containing gel (after centrifugation at 20,000 rpm) and the weight of the dry gel:

Weight of sample swollen with toluene (wet weight) QI

Weight of the toluene-free sample (dry weight)

To determine the gel content and swelling index, 250 mg of gel in 25 ml are left

Swell the toluene with shaking for 24 h. The gel is centrifuged off and weighed and then dried to constant weight at 70 ° C. and weighed again.

The glass transition temperature (Tg) of the rubber gels is between -70 ° C and + 10 ° C. It is determined using DSC (Differential Scanning Calorimetry) (e.g. calorimeter

Pyris DSC-7 from Perkin-Elmer). For the determination of Tg 11.6 + 0.3 mg substance are used in normal capsules. Two heats are carried out, each from -100 ° C to + 150 ° C at a heating rate of 20K / min and a cooling rate of 320 IC / min with nitrogen flushing. The glass temperatures are determined during the 2nd DS C heating.

The isocyanatosilanes (C) have the following basic structure:

, in which

R ¹ , R ² and R ^{3 represent} alkoxy groups with 1 to 12 C atoms, preferably 1 to 8 C atoms, and can be the same or different and Q represents a spacer group with structural elements based on aliphatic, heteroaliphatic, aromatic and heteroaromatic carbon chains.

R ¹ , R ² and R ^{3 are} preferably methoxy, ethoxy, propoxy and butoxy groups and Q is methyl, ethyl, propyl, butyl, pentyl and hexyl groups.

The preferred isocyanatoalkoxysilane is gamma-isocyanatopropyltriethoxysilane of the following formula:

This product is e.g. commercially available from Witco under the name Silquest A-1310 Silane.

The rubber mixtures according to the invention can contain additional further components such as fillers.

Particularly suitable fillers for the production of the rubber mixtures and vulcanizates according to the invention are:

- soot. The carbon blacks to be used here are produced by the soot, furnace or gas black process and have BET surface areas of 20-200 m ² / g such as: S AF-IS AF, IIS AF, HAF, FEF or GPF -Russian.

- highly disperse silica, produced for example by precipitation of solutions of silicates or Flammliydrolse of silicon halogens with specific surface areas of 5-1000, preferably 20-400 m ² / g (BET surface area) and primary particle sizes of 5-400 nm. The silicas can optionally also be mixed oxides with other metal oxides, such as Al, Mg , Ca, Ba, Zn and Ti oxides are present.

- Synthetic silicates, such as aluminum silicate, alkaline earth metal silicate, such as magnesium silicate or calcium silicate with BET surface areas of 20-400 m ² / g and primary particle diameters of 5-400 nm.

- natural silicates, such as kaolin and other naturally occurring silicas.

Metal oxides, such as zinc oxide, calcium oxide, magnesium oxide, aluminum oxide.

Metal carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate.

Metal sulfates such as calcium sulfate, barium sulfate.

Metal hydroxides such as aluminum hydroxide and magnesium hydroxide.

- High melting point thermoplastics, such as trans-l, 4-polybutadiene, syndiotactic 1,2-polybutadiene, polybutylene and polyethylene terephthalate or syndiotactic polystyrene.

- Thermoplastics with high glass transition temperature, such as polyamides, polyphenylene sulfϊd, or polycarbonates.

- Rubber gels based on CR, BR, SBR or all other previously described gel particles, which have a high degree of crosslinking, with a particle size of 5-1000 nm.

Glass fibers and glass fiber products (fibers, strands or micro glass balls). - Thermoplastic fibers (polyamide, polyester, aramid).

The fillers mentioned can be used alone or in a mixture. The amount of the fillers is usually 5 to 200 parts by weight, based on 100

Parts by weight of rubber. In a particularly preferred embodiment of the process, 10-100 parts by weight of rubber gel (B), together with 0.1-100 parts by weight of carbon black and / or 0.1-100 parts by weight of light fillers, are used, based in each case on 100 parts by weight of non-crosslinked rubber. If a mixture of carbon black and light fillers is used, the total amount is a maximum of 100

Parts by weight.

The rubber mixtures according to the invention can contain further rubber auxiliaries, such as crosslinking agents, reaction accelerators, anti-aging agents, heat stabilizers, light stabilizers, ozone protection agents, processing aids, plasticizers, tackifiers, blowing agents, dyes, pigments, wax, extenders, organic acids, retarders, metal oxides and filler activators, such as for example triethanolamine, polyethylene glycol, hexanetriol, bis (triethoxisilylpropyl) tetrasulfide or other auxiliaries known in the rubber industry.

The rubber auxiliaries mentioned are in conventional amounts, which u. a. according to the intended use. Common amounts are e.g. Amounts of 0.1-50 percent by weight, based on the amounts of rubber (A) used.

Cross-linking agents such as sulfur, sulfur donors, peroxides or cross-linking agents such as diisopropenylbenzene, divinylbenzene, divinyl ether, divinyl sulfone, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene, N, N'-m-phenylene-maleimide and / or Triallyl trimellitate can be used. In addition, the acrylates and methacrylates of polyvalent, preferably 2 to 4-valent C to C ₁₀ alcohols, such as ethylene glycol, propanediol-1, 2, butanediol, hexanediol, polyethylene glycol with 2 to 20, preferably 2 to 8, oxy- ethylene units, neopentyl glycol, bisphenol-A, glycerol, trimethyl propane, pentaerythritol, sorbitol with unsaturated polyesters from aliphatic di- and polyols as well as maleic acid, fumaric acid and / or itaconic acid. The amount of crosslinking agent or crosslinking agent is generally 1 to 30 parts by weight, based on 100 parts by weight of the monomers.

The rubber mixtures according to the invention can also contain vulcanization accelerators. Examples of suitable vulcanization accelerators are e.g. Mercaptobenzthiazoles, -sulfenamides, guanidines, thiurams, dithiocarbamates, thioureas and thiocarbonates. The vulcanization accelerators, crosslinkers or other crosslinking agents, such as dimeric 2,4-tolylidene di-isocyanate (- = Desmodur TT) or 1,4-bis (2-hydroxyethoxy) benzene (= crosslinker 30/10 from Rheinchemie) are used in quantities from about 0.1 to 40 percent by weight, preferably 0.1 to 10 percent by weight, based on the total amount of rubber used.

The rubber mixtures according to the invention can be vulcanized at temperatures of 100-250 ° C., preferably 130-180 ° C., if appropriate under a pressure of 10-200 bar.

The mixtures according to the invention can be prepared in various ways.

On the one hand, it is of course possible to mix the solid individual components. Suitable units for this are, for example, roller, internal mixer or mixing extruder. However, mixing by combining the latices of the uncrosslinked or crosslinked rubbers is also possible. The mixture according to the invention thus prepared can be isolated, as usual, by evaporation, precipitation or freeze coagulation (cf. US Pat. No. 2,187,146). By mixing fillers into the latex mixture and subsequent working up, the mixtures according to the invention can be obtained directly as a rubber / filler formulation. The addition of further mixture components to the rubber mixture Double bond-containing rubber (A), rubber gel (B) and isocyantosilane (C) such as additional fillers and, if appropriate, rubber auxiliaries, are carried out in conventional mixing units, rollers, internal mixers or also mixing extruders. The mixing temperatures are around 50-180 ° C.

The rubber mixtures according to the invention are suitable for the production of vulcanized moldings, for example for the production of cable jackets, hoses, drive belts, conveyor belts, roller coverings, shoe soles, sealing rings, damping elements or membranes and for various tire components such as tire treads, sub-tread mixtures, carcasses or Sidewall inserts for tires with run-flat properties.

Examples

Production of the rubber gels

Table 1

¹⁾ Dicumyl peroxide

²⁾ Hydroxyethyl methacrylate ³⁾ Hydroxybutyl acrylate

⁴⁾ swelling index

⁵⁾ Glass temperature

Gel 1: The preparation is carried out as described in US Pat. No. 5,395,891, 1.0 phr (parts per one hundred parts of rubber) being used for crosslinking with dicumyl peroxide.

Gel 2: The preparation is carried out as described in DE patent application No. 19919459.9, yellow drawing I, 1.5 phr of dicumyl peroxide being used for the crosslinking (see la) "Crosslinking of the rubbers present in latex form")

Grafting with hydroxyethyl methacrylate is carried out as described in lb) "Grafting of the Rubbers Present in Latex Form". The stabilization and working up The hydroxyl-modified microgel is carried out as described under point 1c) “Stabilization and working up of the hydroxyl-modified microgels”.

Gel 3: The polymerization of the starting BR latex is carried out as described in US Pat. No. 5,395,891. Networking with DCP, grafting with HEMA and processing are described in the above DE application.

Gel 4: Gel 4 is prepared analogously to gel 3, with hydroxybutyl acrylate (HB A) being used instead of hydroxyethyl methacrylate (HEMA) for the hydroxyl modification.

Compound production, vulcanization and properties of the vulcanizates

In the first mixture series, the effect according to the invention is demonstrated with an unmodified BR gel (gel 1) and with a HEMA-modified SBR rubber gel (gel 2):

For this purpose, the mixture components are mixed on the roller in the specified order according to the following recipes:

Table 2

1) TSR 5, Defo 700 2) Antilux ® 654 from Rheinchemie 3) Vulkanox® 4010 NA from Bayer AG 4) Vulkanox® HS from Bayer AG 5) Enerthene® 1849-1 from BP

After the mixtures have cooled to room temperature (daily storage at room temperature), Vulkacit® NZ and Silquest® A-1310 silanes are mixed in on the roller.

Table 3

6) Vulkacit® NZ Bayer AG 7) Silquest ^® A-1310 Silane from Witco

The vulcanization behavior of the mixtures is examined in a rheometer at 160 ° C according to DIN 53 529. In this way, characteristic data such as F _a , Fmax, Fmax -F _a ., T ₁₀ , t ₈₀ and t _{90 are} determined: Table 4

According to DIN 53 529, Part 3:

F _a : Vulkameter display in the minimum of the crosslinking isotherm

F _max ". Maximum of the vulkameter display tio time at which 10% of the turnover is reached t ₈ o time at which 80% of the turnover is reached t ₉ o time at which 90% of the turnover is reached

The mixtures are vulcanized in the press at 160 ° C.

Table 5

The following test results are obtained on the basis of the above-mentioned compounds:

Table 6

Result: The first series of mixtures shows that the use of γ-isocyanatopropyltriethoxysilane improves the mechanical properties of both a non-hydroxyl-modified BR gel (Gell) and a hydroxymodified SBR gel (Gel 2) (p ₃ oo x D) is achieved.

In the second mixture series, the effect according to the invention is demonstrated for two BR rubber gels containing hydroxyl groups, gel 3 modified with HEMA and gel 4 modified with HBA.

For this purpose, the mixture components according to the following recipes on the

Roller mixed in the order given: Table 8

1) TSR 5, Defo 700

2) Antilux ® 654 from Rheinchemie 3) Vulkanox® 4010 NA from Bayer AG 4) Vulkanox® HS from Bayer AG 5) Enerthene® 1849-1 from BP

After the mixtures have cooled to room temperature (daily storage at room temperature), Vulkacit® NZ and Silquest® A-1310 silanes are mixed in on the roller. Table 9

⁶⁾ Vulkacit® NZ from Bayer AG

⁷⁾ Silquest® Al 310 silanes from Witco

The vulcanization behavior of the mixtures is examined in a rheometer at 160 ° C. In this way, characteristic information, such as F _m i _n, F _m ax.-Fn_in-, tio, t ₈₀ and t o ₉ determined .:

Table 10

The mixtures are vulcanized in the press at 160 ° C.

Table 11

The following test results are obtained on the basis of the above-mentioned compounds: Table 12

In the second mixture series, the improvement of the mechanical properties (S oo D) is demonstrated by the use of γ-isocyanatopropyltriethoxysilane in two BR rubber gels containing hydroxyl groups, with 4 larger BR gel modified with the hydroxybutyl acrylate (HBA) Effects than those obtained with the BR-Gel 3 modified with hydroxethyl methacrylate (HEMA).

Claims

Patentansprtiche

1. rubber mixtures containing at least one double bond-containing rubber (A), at least one microgel (B) and at least one isocyanatosilane (C), the proportion of double bonded rubber (A) being 100

Parts by weight, the proportion of rubber gel (B) is 1 to 150 parts by weight, and the proportion of isocyanatosilane (C) is 0.2 to 20 parts by weight, and optionally rubber auxiliaries and fillers.

2. Rubber mixtures according to claim 1, characterized in that one

NR, BR, SBR, SNBR, IIR and EPDM are used as double-bonded rubbers (A).

3. Rubber mixtures according to claim 1, characterized in that the rubber gels used are BR, NR, NBR, CR or SBR rubber gels, which are optionally modified with surface groups which can react with isocyanatosilanes (C).

4. Rubber mixtures according to claim 3, characterized in that the rubber gels used are those which are modified with hydroxybutyl acrylate.

5. Rubber mixtures according to claim 1, characterized in that γ-isocyanatopropyltriethoxysilane is used as the isocyantosilane.

6. Use of the rubber mixtures according to claim 1 for the production of vulcanized rubber moldings, in particular for the production of tire components.