阅读说明：本技术 氟弹性体可固化的组合物 (Fluoroelastomer curable compositions ) 是由 L·切尔尼舍瓦 L·M·鲍伊盖拉 M·巴西 N·拉涅里 于 2019-02-04 设计创作，主要内容包括：本发明涉及UV可固化的组合物,其包含含碘的(全)氟弹性体、以及明确量的给定的光引发剂与交联剂的某些组合,这些组合物特别有效的使得通过低温UV固化交联的零件具有出色的机械特性。(The present invention relates to UV curable compositions comprising iodine containing (per) fluoroelastomers, and certain combinations of a given photoinitiator and a crosslinking agent in a well-defined amount, these compositions being particularly effective in enabling parts crosslinked by low temperature UV curing to have excellent mechanical properties.)

1. A composition [ composition (C) ] comprising:

-at least one (per) fluoroelastomer comprising iodine cure sites [ fluoroelastomer (a) ];

-at least one photoinitiator [ initiator (P) ] having the formula:

wherein:

each R^A _HAre identical or different from each other and are C₁-C₁₂A hydrocarbon group, possibly containing one or more than one heteroatom, in particular selected from the group consisting of oxygen, nitrogen, sulphur;

-j^Ais zero or an integer from 1 to 3;

-E is a trivalent ═ P (═ O) -group or a trivalent ═ C (R)^D _H) A group in which R^D _HIs methyl or ethyl;

-R^B _His phenyl, methyl or ethyl, with the proviso that when E is ═ C (R)^C _H) When is, then R^B _HIs methyl or ethyl;

-R^C _His a hydrogen atom or is selected from methyl and ethyl; and is

Said initiator (P) being present in an amount of from 4.0 to 15.0phr, based on the fluoroelastomer (A);

and

-at least one polyunsaturated compound [ compound (U) ] selected from (U-1) trisubstituted isocyanurate compounds having the general formula:

wherein each R_isocyAre identical to or different from each other and, at each occurrence, are independently selected from H or a group-R_risocyOR-OR_risocyWherein R is_risocyIs C₁-C₅Alkyl, possibly containing one or more halogens, and each J_isocyAre identical to or different from each other and, at each occurrence, are independently selected from a bond or a divalent hydrocarbon group, optionally comprising heteroatoms; and

(U-2) a tri-substituted cyanurate compound having the general formula:

wherein each R_cyAre identical to or different from each other and, at each occurrence, are independently selected from H or a group-R_rcyOR-OR_rcyWherein R is_rcyIs C₁-C₅Alkyl, possibly containing one or more halogens, and each J_cyAre identical to or different from each other and, at each occurrence, are independently selected from a bond or a divalent hydrocarbon group, optionally comprising heteroatoms;

the compound (U) is present in an amount of from 2.5 to 15.0phr, based on the fluoroelastomer (A).

2. The composition (C) according to claim 1, wherein said at least one photoinitiator (P) is at least one photoinitiator [ initiator (P-1) ] having the formula:

wherein:

-R¹ _Hand R² _HIdentical to or different from each other, independently methyl or ethyl, preferably both methyl;

each R³ _HAre mutually connectedSame or different is C₁-C₁₂A hydrocarbon group, possibly containing one or more than one heteroatom, in particular selected from the group consisting of oxygen, nitrogen, sulphur; and is

-j is zero or an integer from 1 to 3, preferably it is zero,

the initiator (P-1) is present in an amount of from 4.0 to 15.0phr, based on the fluoroelastomer (A).

3. The composition (C) according to claim 1, wherein said at least one photoinitiator is at least one photoinitiator [ initiator (P-2) ] having the formula:

wherein:

each R^1’ _HAre identical or different from each other and are C₁-C₁₂A hydrocarbon group, possibly containing one or more than one heteroatom, in particular selected from the group consisting of oxygen, nitrogen, sulphur;

-R^2’ _His a group selected from methyl, ethyl and phenyl;

-R^3’ _His a group selected from methyl and ethyl;

-j' is zero or an integer from 1 to 3, preferably it is zero,

the initiator (P) is present in an amount of 4.0 to 15.0phr, based on the fluoroelastomer (a).

4. Composition (C) according to any one of the preceding claims, wherein said fluoroelastomer (A) comprises recurring units derived from at least one (per) fluorinated monomer selected from the group consisting of:

-C₂-C₈fluoro-and/or perfluoroolefins, such as Tetrafluoroethylene (TFE), Hexafluoropropylene (HFP), pentafluoropropene, and hexafluoroisobutylene;

-C₂-C₈hydrogenated monofluoroolefins, such as vinyl fluoride;

-1, 2-difluoroethylene, vinylidene fluoride (VDF), and trifluoroethylene (TrFE);

-corresponds to the formula CH₂＝CH-R_f0Of (per) fluoroalkylethylenes of (a), wherein R_f0Is C₁-C₆(per) fluoroalkyl or C with one or more ether groups₁-C₆(per) fluorooxyalkyl;

-chloro-and/or bromo-and/or iodo-C₂-C₆Fluoroolefins like Chlorotrifluoroethylene (CTFE);

-corresponds to the formula CF₂＝CFOR_f1Fluoroalkyl vinyl ether of (2), wherein R_f1Is C₁-C₆Fluoro-or perfluoroalkyl, e.g. -CF₃、-C₂F₅、-C₃F₇；

-corresponds to the formula CH₂＝CFOR_f1In which R is_f1Is C₁-C₆Fluoro-or perfluoroalkyl, e.g. -CF₃、-C₂F₅、-C₃F₇；

-corresponds to the formula CF₂＝CFOX₀In which X is₀Is C₁-C₁₂Oxyalkyl or C with one or more ether groups₁-C₁₂(per) fluorooxyalkyl; more particularly according to formula CF₂＝CFOCF₂OR_f2Of (per) fluoro-methoxy-vinyl ether of (meth), wherein R_f2Is C₁-C₆Fluoro-or perfluoroalkyl, e.g. -CF₃、-C₂F₅、-C₃F₇Or C having one or more ether groups₁-C₆(per) fluorooxyalkyl, like-C₂F₅-O-CF₃；

-corresponds to the formula CF₂＝CFOY₀Functional fluoro-alkyl vinyl ethers of (a), wherein Y₀Is C₁-C₁₂Alkyl or (per) fluoroalkyl, or C₁-C₁₂Oxyalkyl or C₁-C₁₂(per) fluorooxyalkyl, said Y₀The groups comprise carboxylic or sulfonic acid groups in their acid, acid halide or salt form;

-a (per) fluorodioxole having the formula:

wherein R is_f3、R_f4、R_f5、R_f6Each of which is the same as or different from each other, independently a fluorine atom, C₁-C₆Fluoro-or per (halo) fluoroalkyl optionally containing one or more oxygen atoms, e.g. -CF₃、-C₂F₅、-C₃F₇、-OCF₃、-OCF₂CF₂OCF₃。

5. Composition (C) according to claim 4, wherein said fluoroelastomer (A) is chosen from:

(1) VDF-based copolymers wherein VDF is copolymerized with at least one additional comonomer selected from the group consisting of:

(a)C₂-C₈perfluoroolefins, such as Tetrafluoroethylene (TFE), Hexafluoropropylene (HFP);

(b) containing hydrogen C₂-C₈Olefins, such as Vinyl Fluoride (VF), trifluoroethylene (TrFE), Hexafluoroisobutylene (HFIB), of formula CH₂＝CH-R_fWherein R is_fIs C₁-C₆A perfluoroalkyl group;

(c) c comprising at least one of iodine, chlorine and bromine₂-C₈Fluoroolefins, such as Chlorotrifluoroethylene (CTFE);

(d) having the formula CF₂＝CFOR_f(per) fluoroalkyl vinyl ethers (PAVE) of (a), wherein R_fIs C₁-C₆(per) fluoroalkyl, preferably CF₃、C₂F₅、C₃F₇；

(e) Having the formula CF₂(per) fluoro-oxy-alkyl vinyl ethers of CFOX, wherein X is C comprising catenary oxygen atoms₁-C₁₂((per) fluoro) -oxyalkyl, such as perfluoro-2-propoxypropyl;

(f) (per) fluorodioxoles having the formula:

wherein R is_f3、R_f4、R_f5、R_f6Each of which is the same or different from each other, independently selected from the group consisting of: fluorine atom and C optionally containing one or more than one oxygen atom₁-C₆(per) fluoroalkyl groups, notably like-CF₃、-C₂F₅、-C₃F₇、-OCF₃、-OCF₂CF₂OCF₃(ii) a Preferably, perfluorodioxoles;

(g) (per) fluoro-methoxy-vinyl ether (MOVE, herein after) having the formula:

CF₂＝CFOCF₂OR_f2

wherein R is_f2Selected from the group consisting of: c₁-C₆(per) fluoroalkyl; c₅-C₆A cyclic (per) fluoroalkyl group; and C containing at least one catenary oxygen atom₂-C₆(per) fluorooxyalkyl; r_f2Preferably is-CF₂CF₃(MOVE1)；-CF₂CF₂OCF₃(MOVE 2); or-CF₃(MOVE3)；

(h)C₂-C₈Non-fluorinated olefins (Ol), such as ethylene and propylene; and

(2) TFE-based copolymers, wherein TFE is copolymerized with at least one additional comonomer selected from the group consisting of: as described in detail above for (c), (d), (e), (g), (h) and (i).

6. Composition (C) according to any one of the preceding claims, wherein fluoroelastomer (a) comprises iodine cure sites in an amount such that the iodine content is from 0.04 to 10.0% wt, relative to the total weight of fluoroelastomer (a).

7. Composition (C) according to any one of the preceding claims, wherein compound (U) is selected from the group consisting of triallyl isocyanurate (otherwise known as "TAIC") and trivinyl isocyanurate.

8. The composition of any one of the preceding claims, wherein the amount of the compound (U) ranges from 0.1 to 20 parts by weight per 100 parts by weight (phr) of fluoroelastomer (a), preferably from 1 to 15 parts by weight per 100 parts by weight of fluoroelastomer (a), more preferably from 1 to 10 parts by weight per 100 parts by weight of fluoroelastomer (a).

9. Composition (C) according to any one of the preceding claims, additionally comprising: at least one organic solvent, preferably selected from the group consisting of: ketone solvents such as acetone, methyl ethyl ketone; polar solvents such as acetonitrile, Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP); esters such as ethyl acetate; ethers such as tetrahydrofuran, 1, 4-dioxane, and the like.

10. The composition (C) according to any one of the preceding claims, wherein it comprises at least one plasticizer, preferably selected from the group consisting of ester-based plasticizers, such as glutarates (e.g. diisodecyl glutarate), adipates (e.g. bis (2-ethylhexyl) adipate, dimethyl adipate, monomethyl adipate, dioctyl adipate, dibutoxyethoxyethyl adipate, dibutoxyethyl adipate, diisodecyl adipate), maleates (e.g. dibutyl maleate, diisobutyl maleate), azelates, sebacates (e.g. dibutyl sebacate, di-2-ethylhexyl sebacate), trimellitates (e.g. tri-2-ethylhexyl trimellitate), citrates (e.g. triethyl citrate, tributyl citrate), esters of adipic acid, di-n-butyl adipate, di-n-butyl sebacate, tri-n-2-ethylhexyl sebacate, trimellitates, Acetyl triethyl citrate, acetyl tributyl citrate, trioctyl citrate, acetyl trioctyl citrate, trihexyl citrate, acetyl trihexyl citrate), phosphate esters (e.g., triethyl phosphate, tributyl phosphate, trioctyl phosphate).

11. A process for the manufacture of a shaped article, which comprises curing the composition (C) as defined in any one of claims 1 to 13.

12. Cured article obtained from the composition (C) according to any one of claims 1 to 13.

Technical Field

The present invention relates to certain fluoroelastomer compositions having the ability to crosslink at low temperatures, to a process for their manufacture, to a process for their curing and to cured articles shaped therefrom.

Background

Vulcanized (per) fluoroelastomers are materials with excellent heat and chemical resistance characteristics, which are generally used for the manufacture of various sealing articles, such as oil seals, gaskets, shaft seals, and O-rings, wherein the tightness, mechanical properties and resistance to substances with different properties (such as mineral oils, hydraulic fluids, solvents or chemical agents) must be ensured over a wide operating temperature range from low to high temperatures, and wherein the materials may be required to meet stringent requirements in terms of purity, plasma resistance and particle release.

However, in order for (per) fluoroelastomers to exhibit these particular characteristics and advantages, fairly severe curing conditions must be applied to convert viscous rubbery or even viscous fluoroelastomer precursors into cured or vulcanized materials.

While curing at high temperatures is common for rubbers such as nitrile rubber, silicone rubber, acrylic rubber, it is generally believed that the curing temperature of (per) fluoroelastomers is typically higher than the curing temperature of non-fluorocarbon elastomers, and typically ranges from about 160 ℃ to about 180 ℃ or even over 180 ℃.

Due to the high temperatures required to cure (per) fluoroelastomers, compounds containing (per) fluoroelastomers are difficult to mold or process with other plastics or other types of elastomers, for example in a multiple-shot molding process, and it is difficult to apply "in-situ cure" techniques.

In fact, in the art of assembling automobile engines and related mechanical parts such as oil pans and transmissions, silicone sealing materials known as liquid gaskets are used around the flanges to prevent gas and oil from leaking therethrough. Liquid gasket material is typically applied in bead form to one of the mating surfaces to be sealed using an applicator robot. Either before or after curing, the beads are pressed between the mating faces to form the gasket in situ. The gasket sealing system so obtained is commonly referred to as a Formed In Place Gasket (FIPG). Since FIPG contributes to energy saving, resource saving, reduction in part size and weight, and reduction in processing steps, it is used in many industrial fields as well as in the automobile industry. For rubber materials compatible with processing requirements for FIPG, low cure temperature and high cure speed, along with the ability to provide gaskets with heat and chemical resistance (such as resistance to engine oil, gear oil, transmission oil, or LLC depending on the area in which they are used) are of course key factors. While (per) fluoroelastomers are certainly excellent candidates from a performance standpoint, there are deficiencies in their ability to be handled and cured in a manner as readily achievable with silicone-based sealants.

Under these circumstances, attempts have been made in the art to provide solutions for the efficient curing of (per) fluoroelastomers at lower temperatures using UV radiation. US 6803391 (DUPONT dow elastomer LLC) 12/10/2004 discloses compositions which are curable by the action of UV radiation and are thermally stable under processing conditions, wherein the compositions are prepared from a fluoroelastomer having a cure site (e.g. an iodine, chlorine or bromine containing group), a multifunctional crosslinker, and a UV initiator; this document teaches that preferably between 0.5 and 2.5 weight percent, most preferably between 0.5 and 1.0 weight percent of UV initiator is used, since high levels of photoinitiator tend to interfere with penetration and are substantially detrimental to overall crosslink density. The working example of this document provides a fluoroelastomer compound based on a bromine-containing fluoroelastomer, trimethylolpropane triacrylate as a crosslinking agent, and 0.5 parts by weight of 1-hydroxycyclohexylphenylketone and bis (2, 6-dimethoxybenzoyl) -2,4, 4-trimethylbenzophenonePhenylphosphine oxides as

Photoinitiators are commercially available). These compounds suffer from coloring problems due to the presence of bromine during a somewhat reduced mechanical properties of the cured material resulting therefrom; further, the presence of such acrylic groups exposes the cured material to thermal degradation problems due to the use of acrylate-based crosslinkers.

Further, US 6974845 (DAIKIN INDUSTRIES, LTD.) 13/12/2005 discloses a uv-crosslinkable polymer composition comprising a fluoroelastomer having an iodine group, a photoinitiator, and a polyfunctional unsaturated compound. The working examples of this document are notably representative of compounds in which an iodine-containing fluoroelastomer is mixed with a photoinitiator selected from the group consisting of 1-hydroxycyclohexyl phenyl ketone, 2-dimethoxy-2-propiophenone, and benzophenone, a polyfunctional unsaturated compound selected from trimethylolpropane triacrylate and triallyl isocyanurate; all these compounds, once cured by UV radiation, result in cured parts having low strength at 100% elongation and very large elongation at break, i.e. having poor mechanical properties.

WO 2008/019078 (DUPONT DE NEMOURS) 14/02/2008 relates to low refractive index compositions having utility as anti-reflective coatings for optical display substrates, which are the reaction product of a fluoroelastomer, a crosslinker, an oxysilane, an initiator, and a solid nanosilica.

Today, there are still deficiencies in the art for fluoroelastomer compounds having the ability to cure at low temperatures under UV radiation, which will result in cured parts having improved mechanical properties, notably including tensile strength exceeding 5MPa and at the same time elongation at break between about 150% and 300%.

The present invention provides compositions of (per) fluoroelastomers that can be rapidly cured at low temperatures under UV radiation, without impairing the mechanical characteristics of the articles derived from these compositions. These (per) fluoroelastomers may also exhibit low viscosities, which may be useful in grinding and molding applications as well as in-situ curing applications. The compositions of the present disclosure may also include one or more conventional adjuvants, such as, for example, fillers, acid acceptors, processing aids, or dyes.

Disclosure of Invention

The applicant has now found that certain UV-curable compositions comprising (per) fluoroelastomers containing iodine, together with certain combinations of a given photoinitiator in a well-defined amount with a crosslinking agent, can solve the above-mentioned problems and are particularly effective in allowing parts crosslinked by low-temperature UV curing to have excellent mechanical properties.

Accordingly, the present invention relates to a composition [ composition (C) ] comprising:

-at least one (per) fluoroelastomer comprising iodine cure sites [ fluoroelastomer (a) ];

-at least one photoinitiator [ initiator (P) ] having the formula:

wherein:

each R^A _HAre identical or different from each other and are C₁-C₁₂A hydrocarbon group, possibly containing one or more than one heteroatom, in particular selected from the group consisting of oxygen, nitrogen, sulphur;

-j^Ais zero or an integer from 1 to 3;

-E is a trivalent ═ P (═ O) -group or a trivalent ═ C (R)^D _H) A group in which R^D _HIs methyl or ethyl;

-R^B _His phenyl, methyl or ethyl, with the proviso that when E is ═ C (R)^C _H) When is, then R^B _HIs methyl or ethyl;

-R^C _His a hydrogen atom or is selected from methyl and ethyl; and is

Said initiator (P) being present in an amount of from 4.0 to 15.0phr, based on the fluoroelastomer (A);

and

-at least one polyunsaturated compound [ compound (U) ] selected from (U-1) trisubstituted isocyanurate compounds having the general formula:

wherein each R_isocyAre identical to or different from each other and, at each occurrence, are independently selected from H or a group-R_risocyOR-OR_risocyWherein R is_risocyIs C₁-C₅Alkyl, possibly containing one or more halogens, and each J_isocyAre identical to or different from each other and, at each occurrence, are independently selected from a bond or a divalent hydrocarbon group, optionally comprising heteroatoms; and

(U-2) a tri-substituted cyanurate compound having the general formula:

wherein each R_cyAre identical to or different from each other and, at each occurrence, are independently selected from H or a group-R_rcyOR-OR_rcyWherein R is_rcyIs C₁-C₅Alkyl, possibly containing one or more halogens, and each J_cyAre identical to or different from each other and, at each occurrence, are independently selected from a bond or a divalent hydrocarbon group, optionally comprising heteroatoms;

the compound (U) is present in an amount of from 2.5 to 15.0phr, based on the fluoroelastomer (A).

The applicant has unexpectedly found that the above specified amounts of the above specified compounds (i.e. polyunsaturated compounds based on isocyanurates and short-chain substituted (R) which cause homolytic cleavage and notably form a high reactivity) are specified in the above detailed amounts^B _H)(R^D _H)C(OR^C _H) Carbon radical or highly reactive phosphorus-based (R)^B _H)P(＝O)(OR^C _H) Free radical photoinitiators) is such that a curable blend is provided which after UV exposure provides a polymer with a high crosslinking density (in the UV)XL fraction of more than 85% after exposure), high modulus at 100% elongation (typically equal to or more than 4MPa), and suitable elongation at break (typically at least 150% and up to 300%). Furthermore, the use of polyunsaturated compounds (U) comprising highly thermally stable cyanurate or isocyanurate rings as detailed above is such as to ensure good coloration in the final part without degradation and/or discoloration phenomena.

For the purposes of the present invention, the term "(per) fluoroelastomer" [ fluoroelastomer (a) ] is intended to denote a fluoropolymer resin which acts as the base for obtaining a true elastomer, said fluoropolymer resin comprising more than 10% wt, preferably more than 30% wt, of recurring units derived from at least one ethylenically unsaturated monomer containing at least one fluorine atom (hereinafter, (per) fluorinated monomer) and, optionally, recurring units derived from at least one ethylenically unsaturated monomer free from fluorine atoms (hereinafter, hydrogenated monomer).

True elastomers are defined by ASTM, Special Technical Bulletin, standard No.184 (Special Technical Bulletin, No.184 standard) as materials that can be stretched to twice their natural length at room temperature and recover within 10% of their original length within the same time once they are released after being held under tension for 5 minutes.

Generally, the fluoroelastomer (a) comprises recurring units derived from at least one (per) fluorinated monomer, wherein said (per) fluorinated monomer is generally selected from the group consisting of:

-C₂-C₈fluoro-and/or perfluoroolefins, such as Tetrafluoroethylene (TFE), Hexafluoropropylene (HFP), pentafluoropropene, and hexafluoroisobutylene;

-C₂-C₈hydrogenated monofluoroolefins, such as vinyl fluoride; 1, 2-difluoroethylene, vinylidene fluoride (VDF) and trifluoroethylene (TrFE);

-corresponds to the formula CH₂＝CH-R_f0Of (per) fluoroalkylethylenes of (a), wherein R_f0Is C₁-C₆(per) fluoroalkyl or C with one or more ether groups₁-C₆(per) fluorooxyalkyl;

-chloro-and/or bromo-and/or iodo-C₂-C₆Fluoroolefins like Chlorotrifluoroethylene (CTFE);

-corresponds to the formula CF₂＝CFOR_f1Fluoroalkyl vinyl ether of (2), wherein R_f1Is C₁-C₆Fluoro-or perfluoroalkyl, e.g. -CF₃、-C₂F₅、-C₃F₇；

-corresponds to the formula CH₂＝CFOR_f1In which R is_f1Is C₁-C₆Fluoro-or perfluoroalkyl, e.g. -CF₃、-C₂F₅、-C₃F₇；

-corresponds to the formula CF₂＝CFOX₀In which X is₀Is C₁-C₁₂Oxyalkyl or C with one or more ether groups₁-C₁₂(per) fluorooxyalkyl; more particularly according to formula CF₂＝CFOCF₂OR_f2Of (per) fluoro-methoxy-vinyl ether of (meth), wherein R_f2Is C₁-C₆Fluoro-or perfluoroalkyl, e.g. -CF₃、-C₂F₅、-C₃F₇Or C having one or more ether groups₁-C₆(per) fluorooxyalkyl, like-C₂F₅-O-CF₃；

-corresponds to the formula CF₂＝CFOY₀Functional fluoro-alkyl vinyl ethers of (a), wherein Y₀Is C₁-C₁₂Alkyl or (per) fluoroalkyl, or C₁-C₁₂Oxyalkyl or C₁-C₁₂(per) fluorooxyalkyl, said Y₀The groups comprise carboxylic or sulfonic acid groups in their acid, acid halide or salt form;

-a (per) fluorodioxole having the formula:

wherein R is_f3、R_f4、R_f5、R_f6Each of which is the same as or different from each other, independently a fluorine atom, C₁-C₆Fluoro-or per (halo) fluoroalkyl optionally containing one or more oxygen atoms, e.g. -CF₃、-C₂F₅、-C₃F₇、-OCF₃、-OCF₂CF₂OCF₃。

Examples of hydrogenated monomers are notably hydrogenated alpha-olefins, including ethylene, propylene, 1-butene, diene monomers, styrene monomers, typically alpha-olefins are used.

The fluoroelastomer (A) is an amorphous product overall or has a low crystallinity (crystalline phase less than 20% by volume) and a glass transition temperature (T) below room temperature_g) The product of (1). In most cases, the fluoroelastomer (A) advantageously has a T of less than 10 ℃, preferably less than 5 ℃, more preferably 0 ℃_g。

The fluoroelastomer (a) is preferably selected from:

(1) VDF-based copolymers wherein VDF is copolymerized with at least one additional comonomer selected from the group consisting of:

(a)C₂-C₈perfluoroolefins, such as Tetrafluoroethylene (TFE), Hexafluoropropylene (HFP);

(b) containing hydrogen C₂-C₈Olefins, such as Vinyl Fluoride (VF), trifluoroethylene (TrFE), Hexafluoroisobutylene (HFIB), of formula CH₂＝CH-R_fWherein R is_fIs C₁-C₆A perfluoroalkyl group;

(c) c comprising at least one of iodine, chlorine and bromine₂-C₈Fluoroolefins, such as Chlorotrifluoroethylene (CTFE);

(d) having the formula CF₂＝CFOR_f(per) fluoroalkyl vinyl ethers (PAVE) of (a), wherein R_fIs C₁-C₆(per) fluoroalkyl, preferably CF₃、C₂F₅、C₃F₇；

(e) Having the formula CF₂(per) fluoro-oxy-alkyl vinyl ethers of CFOX, wherein X is a group comprising catenary oxygen atomsC₁-C₁₂((per) fluoro) -oxyalkyl, such as perfluoro-2-propoxypropyl;

(f) (per) fluorodioxoles having the formula:

wherein R is_f3、R_f4、R_f5、R_f6Each of which is the same or different from each other, independently selected from the group consisting of: fluorine atom and C optionally containing one or more than one oxygen atom₁-C₆(per) fluoroalkyl groups, notably like-CF₃、-C₂F₅、-C₃F₇、-OCF₃、-OCF₂CF₂OCF₃(ii) a Preferably, perfluorodioxoles;

(g) (per) fluoro-methoxy-vinyl ether (MOVE, herein after) having the formula:

CF₂＝CFOCF₂OR_f2

wherein R is_f2Selected from the group consisting of: c₁-C₆(per) fluoroalkyl; c₅-C₆A cyclic (per) fluoroalkyl group; and C containing at least one catenary oxygen atom₂-C₆(per) fluorooxyalkyl; r_f2Preferably is-CF₂CF₃(MOVE1)；-CF₂CF₂OCF₃(MOVE 2); or-CF₃(MOVE3)；

(h)C₂-C₈Non-fluorinated olefins (Ol), such as ethylene and propylene; and

(2) TFE-based copolymers, wherein TFE is copolymerized with at least one additional comonomer selected from the group consisting of: as described in detail above for (c), (d), (e), (g), (h) and (i).

Optionally, the fluoroelastomers (A) OF the present invention may also comprise a fluoroolefin derived from a bis-olefin [ bis-Olefin (OF) having the general formula]The repeating unit of (a):wherein R is₁、R₂、R₃、R₄、R₅And R₆Are identical or different from each other and are H or C₁-C₅An alkyl group; z is a linear or branched C optionally containing oxygen atoms, preferably at least partially fluorinated₁-C₁₈(hydro) carbon groups (including alkylene or cycloalkylene groups), or (per) fluoro (poly) oxyalkylene groups containing one or more catenary ether linkages.

The bis-Olefin (OF) is preferably selected from the group consisting OF: those complying with formulae (OF-1), (OF-2) and (OF-3):

(OF-1)

wherein j is an integer between 2 and 10, preferably between 4 and 8, and R1, R2, R3, R4, equal to or different from each other, are H, F or C_1-5Alkyl or (per) fluoroalkyl;

(OF-2)

wherein each a, the same or different from each other and at each occurrence, is independently selected from F, Cl, and H; each B is the same OR different from each other and, at each occurrence, is independently selected from F, Cl, H, and OR_BWherein R is_BIs a branched or straight chain alkyl group which may be partially, substantially or fully fluorinated or chlorinated; e is an optionally fluorinated divalent radical having 2 to 10 carbon atoms which may be interrupted by ether linkages; preferably E is- (CF)₂)_m-a group, wherein m is an integer from 3 to 5; a preferred bis-olefin OF the type (OF-2) is F₂C＝CF-O-(CF₂)₅-O-CF＝CF₂。

(OF-3)

Wherein E, A and B have the same meaning as defined above; r5, R6 and R7 are the same or different and are H, F or C_1-5Alkyl or (per) fluoroalkyl.

According to certain preferred embodiments, the fluoroelastomer (a) has a number average molecular weight advantageously of at least 3000 and/or advantageously of at most 45000.

The use of a fluoroelastomer (a) having the above molecular weight and therefore low viscosity makes the composition (C) particularly suitable for processing by liquid injection moulding, screen printing and/or in situ formation techniques. The challenge faced with the use of these techniques is in fact to simultaneously achieve, during roll coating and/or in the dispenser nozzle, a suitably low liquid viscosity of the fluoroelastomer (a), advantageously ensuring a suitable flow of the material in the mould; while also ensuring excellent curability to provide a final article with the required mechanical and sealing properties at reasonable productivity and in reasonably mild processing conditions.

Number average molecular weight (M)_n) Mathematically defined as:

wherein N is_iIs of length M_iThe number of moles of the chain of (a); the number average molecular weight is typically determined by GPC against monodisperse polystyrene standards using Tetrahydrofuran (THF) as the eluent.

Another molecular parameter which can be determined by GPC is notably the weight average molecular weight (M)_w)：

And is

Polydispersity index (PDI), which is expressed herein as the weight average molecular weight (M)_w) And number average molecular weight (M)_n) The ratio of (a) to (b).

The fluoroelastomer (a) of this embodiment has a number average molecular weight of preferably at least 5000, more preferably at least 6000, even more preferably at least 10000.

The fluoroelastomer (a) of this embodiment has a number average molecular weight preferably of at most 40000, more preferably of at most 35000, even more preferably of at most 30000.

According to other preferred embodiments, the fluoroelastomer (a) has a number average molecular weight exceeding 45000, preferably between 50000 and 500000. Fluoroelastomers of this type may be processed by conventional techniques and/or may be combined with solvents or plasticizers for promoting flow.

As mentioned, the fluoroelastomer (a) comprises iodine cure sites.

The amount of iodine and/or bromine cure sites is generally such that the iodine content is from 0.04 to 10.0% wt, relative to the total weight of the fluoroelastomer (a).

These iodine cure sites may be included as side groups bound to the backbone of the fluoroelastomer (a) polymer chain or may be included as end groups of said polymer chain.

According to a first embodiment, the iodine cure site is included as a pendant group bound to the backbone of the fluoroelastomer (a) polymer chain; the fluoroelastomer (a) according to this example typically comprises repeating units derived from brominated and/or iodinated cure site comonomers selected from:

-iodo α -olefins containing from 2 to 10 carbons;

iodofluoroalkylvinyl ethers (as notably described in patents US 454662, US 4564662 (MINNESOTA MINING) 14/01/1986 and EP 199138 a (daikin corporation (DAIKIN IND LTD)) 29/10/1986).

According to a second preferred embodiment, the iodine cure sites are included as end groups of the fluoroelastomer (a) polymer chain; the fluoroelastomer according to this embodiment is generally obtained by adding at least one of the following to the polymerization medium during the manufacture of fluoroelastomer (a):

-one or more iodinated chain transfer agents; suitable chain transfer agents are typically those having the formula R_f(I)_x(Br)_yWherein R is_fIs a (per) fluoroalkyl or a (per) fluorochloroalkyl group containing from 1 to 8 carbon atoms, and x and y are integers between 0 and 2, with 1. ltoreq. x + y. ltoreq.2 (see, for example, patent US 4243770 (large)Gold industries co ltd) 06/01/1981 and US 4943622 (NIPPON MEKTRONKK) 24/07/1990); and

alkali or alkaline earth iodides, as notably described in patent US 5173553 (ausemont liability ltd (ausion SRL)) 22/12/1992.

Advantageously, to ensure acceptable reactivity, it is generally understood that the content of iodine in the fluoroelastomer (a) should be at least 0.05% wt, preferably at least 0.06% by weight, with respect to the total weight of the fluoroelastomer (a).

On the other hand, the amounts of iodine preferably not more than 7% wt, more precisely not more than 5% wt, or even not more than 4% wt, relative to the total weight of fluoroelastomer (a) are those generally chosen to avoid side reactions and/or adverse effects on thermal stability.

The composition (C) may comprise one or more than one compound (U) as detailed above.

Among the trisubstituted isocyanurate compounds (U-1), triallyl isocyanurate (otherwise referred to as "TAIC"), trivinyl isocyanurate may be notably mentioned, with TAIC being most preferred.

Among the trisubstituted cyanurate compounds (U-2), triallyl cyanurate and trivinyl cyanurate may be notably mentioned.

Preferably, compound (U) is TAIC.

The amount of compound (U) is generally in the range from 2.5 to 15.0 parts by weight per 100 parts by weight (phr) of fluoroelastomer (a), preferably from 3.0 to 12 parts by weight per 100 parts by weight of fluoroelastomer (a), more preferably from 3.0 to 10 parts by weight per 100 parts by weight of fluoroelastomer (a).

According to a first embodiment, said at least one photoinitiator (P) is at least one photoinitiator [ initiator (P-1) ] having the formula:

wherein:

-R¹ _Hand R² _HAre identical or different from each other, aloneIs either methyl or ethyl, preferably both methyl;

each R³ _HAre identical or different from each other and are C₁-C₁₂A hydrocarbon group, possibly containing one or more than one heteroatom, in particular selected from the group consisting of oxygen, nitrogen, sulphur; and is

-j is zero or an integer from 1 to 3, preferably it is zero,

the initiator (P-1) is present in an amount of from 4.0 to 15.0phr, based on the fluoroelastomer (A).

Preferably, the initiator (P-1) is a compound corresponding to the above formula, wherein j is zero and R is¹ _HAnd R² _HI.e. 2-hydroxy-2-methyl-1-phenyl-propan-1-one, notably under the trade name1173 are commercially available, but they may alternatively be supplied from other sources

According to a second embodiment, the composition (C) comprises at least one photoinitiator [ initiator (P-2) of formula]：Wherein:

each R^1’ _HAre identical or different from each other and are C₁-C₁₂A hydrocarbon group, possibly containing one or more than one heteroatom, in particular selected from the group consisting of oxygen, nitrogen, sulphur;

-R^2’ _His a group selected from methyl, ethyl and phenyl;

-R^3’ _His a group selected from methyl and ethyl;

-j' is zero or an integer from 1 to 3, preferably it is zero,

the initiator (P) is present in an amount of 4.0 to 15.0phr, based on the fluoroelastomer (a).

Preferably, the initiator (P-2) is a compound corresponding to the above formula, wherein j is 3 and each R is^1’ _HAre both methyl, said R^1’ _HThe radicals being situated in relation to the carbonyl groupOrtho-and para-groups, R^2’ _HIs phenyl and R^3’ _HIs ethyl, i.e. it is 2,4, 6-trimethylbenzoylphenylphosphinate, notably under the trade nameTPO-L is commercially available, but it may alternatively be supplied from other sources.

The amount of initiator (P) is generally in the range from 4.0 to 15.0 parts by weight per 100 parts by weight (phr) of fluoroelastomer (a), preferably from 5.0 to 12.0 parts by weight per 100 parts by weight of fluoroelastomer (a), more preferably from 6.0 to 10.0 parts by weight per 100 parts by weight of fluoroelastomer (a). Good results have been obtained when an amount of about 9.0phr of initiator (P) is used, based on fluoroelastomer (a).

Composition (C) may further additionally comprise ingredients which may be conventionally used for the curing of fluoroelastomers; more specifically, the composition (C) may further comprise, as a whole:

(a) one or more than one metal basic compound, generally in an amount of from 0.5 to 15.0phr, and preferably from 1 to 10phr, more preferably from 1 to 5phr, with respect to 100 parts by weight of fluoroelastomer (a); the metal base compound is generally selected from the group consisting of: (j) oxides or hydroxides of divalent metals, such as Mg, Zn, Ca or Pb, and (jj) metal salts of weak acids, such as stearates, benzoates, carbonates, oxalates or phosphites of Ba, Na, K, Pb, Ca;

(b) one or more than one acid acceptor other than a metal basic compound, in an amount generally ranging from 0.5 to 15.0phr, and preferably from 1 to 10.0phr, more preferably from 1 to 5phr, with respect to 100 parts by weight of fluoroelastomer (a); these acid acceptors are generally selected from nitrogen-containing organic compounds such as 1, 8-bis (dimethylamino) naphthalene, stearylamine and the like as notably described in EP708797A (dupont) 01/05/1996;

(c) other conventional additives such as fillers, thickeners, pigments, antioxidants, stabilizers, processing aids/plasticizers, and the like.

According to certain embodiments, composition (C) may additionally comprise at least one organic solvent, suitable organic solvents being, but not limited to, ketone solvents such as acetone, methyl ethyl ketone; polar solvents such as acetonitrile, Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP); esters such as ethyl acetate; ethers such as tetrahydrofuran, 1, 4-dioxane, and the like. More preferred solvents are acetone and methyl ethyl ketone.

According to certain embodiments, the composition (C) may comprise at least one plasticizer (P), generally chosen from those known for fluororubbers. The plasticizer (P) will generally be selected from ester-based plasticizers such as glutarates (e.g. diisodecyl glutarate), adipates (e.g. bis (2-ethylhexyl) adipate, dimethyl adipate, monomethyl adipate, dioctyl adipate, dibutoxyethoxyethyl adipate, dibutoxyethyl adipate, diisodecyl adipate), maleates (e.g. dibutyl maleate, diisobutyl maleate), azelates, sebacates (e.g. dibutyl sebacate, di-2-ethylhexyl sebacate), trimellitates (e.g. tri-2-ethylhexyl trimellitate), citrates (e.g. triethyl citrate, tributyl citrate, acetyl triethyl citrate, acetyl tributyl citrate, trioctyl citrate, acetyl trioctyl citrate, trihexyl citrate, citric acid, Acetyl trihexyl citrate), phosphate esters (e.g., triethyl phosphate, tributyl phosphate, trioctyl phosphate).

Composition (C) may be prepared by any known mixing method. When the fluoroelastomer (A) is a high-viscosity elastomer, the kneading may be carried out by an internal mixer such as an open roll or a kneader mixer; for low viscosity fluoroelastomers (a), mixing may be more effective when performed in a planetary mixer, a mobile mixer, or the like. Further, when an organic solvent is present as detailed above, mixing may be accomplished by a suitable mixing device (including any agitated vessel) suitable for liquid mixing.

It is generally recommended that composition (C) be prepared without substantial exposure to light energy that may activate initiator (P).

The invention also relates to a process for the manufacture of a shaped article, which comprises curing the composition (C) as described above.

The composition (C) can be manufactured, for example, by molding (injection molding, extrusion molding), calendering, coating, screen printing, in-situ forming into the desired shaped article, which is advantageously subjected to vulcanization (curing) during processing of the shaped article itself and/or in a subsequent step (post-treatment or post-curing); the relatively soft, weak, fluoroelastomer uncured composition is advantageously converted into a finished article made from a non-tacky, strong, insoluble, chemical and heat resistant cured fluoroelastomer material.

The method of the present invention includes curing under exposure to UV radiation.

Suitable ultraviolet rays are those having a wavelength of from 420 to 150nm, preferably from 400 to 200 nm. The wavelength spectrum of the radiation used to carry out the curing reaction will typically be selected to correspond to the absorption maximum of the UV initiator.

Suitable UV sources include medium pressure mercury lamps, electrodeless lamps, pulsed xenon lamps, hybrid xenon/mercury lamps, and Light Emitting Diodes (LEDs) designed to emit radiation in the ultraviolet range.

The radiation dose is generally chosen so as to be sufficient to cure the composition (C); the dosage will generally depend on the distance of the composition (C) from the UV source in its preformed form, the duration of exposure, and the power level of the UV source.

The required radiation dose can be determined by one of ordinary skill in the art based on routine experimentation. Generally, when a UV source providing an output power of about 800W is used, an acceptable degree of cure can be obtained by exposure for a period of 30 to 1000 seconds, preferably 50 to 800 seconds.

The UV curing may be carried out at a temperature of usually not more than 100 ℃, preferably not more than 80 ℃, more preferably not more than 50 ℃.

As already explained, it is a particularly beneficial effect of the present invention that the composition (C) provides the ability to cure the shaped article under UV radiation while avoiding the need to expose the part to be cured to high temperatures.

However, the present invention relates to the cured articles obtained from the composition (C) as detailed above. The cured article is typically obtained by molding and curing the fluoroelastomer composition as detailed above. These cured articles may be sealing articles including O (square) -rings, shims, gaskets, spacers (diaphragm), shaft seals, valve stem seals, piston rings, crankshaft seals, camshaft seals, and oil seals, or may be pipes and tubes, particularly flexible hoses or other items, including conduits for the delivery of hydrocarbon fluids and fuels.

If the disclosure of any patent, patent application, and publication incorporated by reference herein conflicts with the present description to the extent that no ambiguity in terminology is intended, then the present description shall prevail.

The present invention will now be described in more detail with reference to the following examples, which are intended to be illustrative only and not to limit the scope of the present invention.

Examples of the invention

Raw materials

TPO-L is ethyl (2,4, 6-trimethylbenzoyl) phenylphosphinate asTPO-L is commercially available from IGM Resins, Inc. (IGM Resins) and is used as is.

D-1173 is 2-hydroxy-2-methyl-1-phenyl-propan-1-one, supplied by Aldrich and used as such.

D-MBF is methyl phenylglyoxylate (otherwise known as methyl benzoylformate) which is supplied by Sigma Aldrich (Sigma Aldrich) and used as such.

TAIC is triallyl isocyanurate, as

Commercially available from Degussa corporation (Degussa) and used as received.

Fluoroelastomers curable with iodine-containing peroxides asP457 by SollCommercially available from Solvay Specialty Polymers Italy s.p.a.; it will be referred to as (A-2) hereinafter.

Examples of the invention

Preparation example 1-preparation of fluoroelastomer (A-1)

In a 10 liter reactor equipped with a mechanical stirrer operating at 545rpm, 5.4l of demineralized water and 40ml of microemulsion, obtained beforehand by mixing: 8.8ml of a perfluoropolyoxyalkylene having an acidic end group having the formula: CF (compact flash)₂ClO(CF₂-CF(CF₃)O)_n(CF₂O)_mCF₂COOH (where n/m is 10, with a weight average molecular weight of 600), 5.6ml of 30% v/v NH₄Aqueous OH solution, 20.0ml demineralized water and 5.5ml of a solution of the formula

D02 perfluoropolyether: CF (compact flash)₃O(CF₂CF(CF₃)O)_n(CF₂O)_mCF₃(wherein n/m is 20, having a weight average molecular weight of 450). The reactor was heated and maintained at a set point temperature of 80 ℃. A mixture of Tetrafluoroethylene (TFE) (11 mol%), vinylidene fluoride (VDF) (70 mol%) and Hexafluoropropylene (HFP) (19 mol%) was then added to reach a final pressure of 30 bar (3.0 MPa). 54ml of 1, 4-diiodoperfluorobutane (C) as chain transfer agent were then introduced₄F₈I₂) And 1.8g Ammonium Persulfate (APS) as an initiator. The pressure was maintained at the 30 bar set point by continuously feeding a gaseous mixture of TFE (11 mol%), VDF (70 mol%) and HFP (19 mol%) until a total of 3150 g. The reactor was then cooled, vented, and the latex recovered. The latex was dried under vacuum on a rotary evaporator until the liquid phase was completely removed to recover the polymer.

The fluoroelastomer having the following molar composition was thus recovered: TFE: 12.0% by mole; VDF: 70.5% mol; HFP: 17.5 mol% iodine, 2.3 wt%. When the fluoroelastomer was analyzed by GPC, by dissolving a sample thereof in tetrahydrofuran at a concentration of about 0.5% wt/vol for 6 hours at room temperature under magnetic stirring; the solution thus obtained was filtered through a PTFE filter having a pore size of 0.45 μm, and the filtered solution was injected into a GPC system; details of GPC conditions are listed below:

mobile phase tetrahydrofuran; the flow rate is 1.0 mL/min; the temperature is 35 ℃; injection system auto-injector model 717 plus; injection volume 200 μ l; pump no gradient pump model 515; column setting: front bar +4 Watts (Waters) Styragel HR: 10⁶、10⁵、10⁴Andrefractive index model 2414 from detector Waters (Waters); software for data acquisition and processing: wottish Empower 3. The fluoroelastomer was found to have an M of 12398_n23355M_wAnd a polydispersity index of 1.9; substantially no fraction with a molecular weight below 1000 was found.

The mooney viscosity measured at 121 ℃ (1+10min) according to ASTM D1646 provides an unmeasurable value, more precisely a value below the detection limit of the instrument, demonstrating a very low viscosity as related to molecular weight.

Mixing and crosslinking procedure

The fluoroelastomer of preparation example 1 was mixed with the additives as specified in the following table according to the procedure detailed below.

The general procedure for final sheet preparation for characterization included: the polymer is mixed with the curing agent and the initiator that initiates curing until fully homogenized. Mixing is carried out by hand mixing or in a high speed mixer or in a stirred vessel in the solvent.

Specifically, in a 100ml glass Becker equipped with a magnetic stirrer, when the composition contains a solvent, the ingredients are introduced according to the following procedure: dissolving the fluoroelastomer in a solvent at 40 ℃ and stirring at 600rpm until the fluoroelastomer is completely dissolved; the polyfunctional compound and photoinitiator are then added and homogenization of the blend is carried out over a period of 5 minutes. The composition was then poured onto a petri dish and dried in a static oven at 40 ℃ to remove the solvent. The dried compound is then cured by ultraviolet irradiation.

When the composition does not contain any solvent, a SpeedMixer is used^TMBladeless centrifugal mixer equipment, model DAC400 FVZ, available from FlackTek Inc. All the ingredients of the composition (fluoroelastomer, polyfunctional compound and photoinitiator) were introduced into a 300ml polypropylene tank and mixed by a SpeedMixer device until fully homogenized. The composition was then poured onto a petri dish and cured by uv irradiation.

Conditions of ultraviolet irradiation

UV curing was carried out in a UV curing apparatus called the "cure test" by Helios Italquartz s.r.i. The "cure test" was equipped with a UV lamp HMPL. HMPL is a medium pressure mercury lamp emitting over the spectrum of ultraviolet light (UVA, UVB and UVC) with a peak emission in the UVA range at 366 nm.

To cure the compound, the sample was placed in a "cure test" and exposed to irradiation under a nitrogen atmosphere. N is a radical of₂The feed was fed at a constant flow of 0.5 bar. The irradiation cycle lasted 9 minutes. The sample temperature was controlled to avoid heating above 50 ℃. The device was used at 100% power illumination (800 watts).

After UV irradiation, the (PC) cured samples can be post-cured. The PC for the cured samples by UV included a static heat treatment at 50 ℃ for 48 hours.

In the following table, the amounts of ingredients are provided in parts by weight based on 100 parts by weight of the fluororubber base.

Determination of mechanical Properties on cured samples

Tensile properties were determined according to ASTM D638 type V standards for samples punched from these stacked films.

M₁₀₀Is the tensile strength in MPa at 100% elongation;

TS is tensile strength in MPa;

EB is the elongation at break in%.

The shore a hardness (3 ") (HDS) was measured according to ASTM D2240 method on 3 substrates stacked.

Evaluation of crosslinking efficiency

In a closed glass vessel, the sample was immersed in MEK (ratio: 1g polymer in 50mL of MEK) for 16 hours (overnight) at room temperature without stirring. A suitable amount of polymer for testing is 2 g.

After impregnation, the samples were dried in an oven under vacuum at 110 ℃ for 4 hours. This drying process is required to evaporate the absorbed liquid and to determine whether partial dissolution of the sample has occurred.

The crosslinking efficiency was then determined as the percent insolubility of the sample as a weight percent between the final weight and the initial weight of the sample.

TABLE 1

Very dark cured samples, mechanical properties not suitable for use as fluororubbers; 1: a composition prepared via a solution process using ethyl acetate as a solvent;²: compositions prepared via solution processes using EFX solvents.

TABLE 2

^1：Compositions prepared via solution process using ethyl acetate as solvent

For comparison, cured samples were prepared by standard mixing (see example 14C) using the same fluoroelastomer raw rubber but adding conventional peroxide curing ingredients and molding at 170 ℃ for 10 minutes followed by post-curing at 230 ℃ for 4 h; the results shown below demonstrate that low temperature UV curing of the compositions of the present invention results in substantially similar product properties.

TABLE 3

^1：Compositions prepared in a SpeedMixer in the absence of a solvent;²：101, 2, 5-bis (tert-butylperoxy) -2, 5-dimethylhexane;³: compositions prepared by hand mixing in the absence of solvent, and UV curing and post-curing according to the procedures described above.