DE102013219785A1 - Sunlight-induced crosslinking of unsaturated polyolefins with unactivated vinylic double bonds - Google Patents

Abstract

The present invention relates to photocrosslinking systems which are activatable by UV or sunlight and whose cross-linked product fluoresces in contrast to the starting materials. The formulation before crosslinking is composed of a component having vinyl groups of the form CH 2 = CHR 3, preferably a polymer such as, for example, 1,2-polybutadiene and a crosslinker having 2H-tetrazol-5-yl benzoate groups.

Description

Field of the invention

The present invention relates to photocrosslinking systems which are activatable by UV or sunlight and whose cross-linked product fluoresces in contrast to the starting materials. In this case, the formulation before crosslinking is composed of a component having vinyl groups of the form CH ₂ = CHR ³ , preferably a polymer such as, for example, 1,2-polybutadiene and a crosslinker having 2H-tetrazol-5-yl benzoate groups.

State of the art

Vinyl group-bearing polymers, especially polyolefins such as 1,2-polybutadienes can be crosslinked by a variety of mechanisms. In addition to the well-known vulcanization with sulfur, especially the crosslinking with photoinitiators, such as acylphosphines or thiocyanato ketones is important. Likewise, direct crosslinking is by means of high-energy UV radiation or with radical initiators such as peroxides or azo-bis-isobutyronitrile (AIBN).

However, there is an additional need to provide fluorescent crosslinked systems. To date, such a task can only be solved by equipping a network with appropriate pigments. However, this embodiment has the disadvantage that pigments can migrate and thus leave the matrix. This can, for example, bring massive problems to dyed elastomers used in children's toys.

Furthermore, there is a need for polymer systems, for example in the form of coatings, which act as a detector when exposed to light and color a light influencing. Such systems may be used as security detectors or, for example, within packages, for example, to indicate a prior opening thereof.

In particular, however, there is a very great interest in daylight-crosslinking systems which are storage-stable without exposure to light and, after application simply by solar radiation or by targeted irradiation, e.g. can be cured with a UV lamp.

task

In view of the state of the art, the object was therefore to provide a photocrosslinking system for polymers which can be crosslinked quickly and easily with daylight.

In addition, the object was to provide a polymeric system which indicates colorless present after contact with light, in particular with daylight, this contact.

Furthermore, the object was to provide a polymeric system which fluoresces after crosslinking.

Other tasks not explicitly mentioned may arise from the description, the examples and the claims of this application.

solution

The objects are achieved with a novel, photo-induced crosslinkable formulation which contains a component A which has at least two vinyl groups of the form CH 2 = CHR 3, where R 3 is a polymer or oligomer having the vinyl groups. Furthermore, the formulation contains a second component B having the following structure

R ₁ is an amine group, a halogen or an ether group -OR ₄ with R ₄ selected from polyethers or linear or branched alkyl groups having 1 to 20 carbon atoms, R ₂ is a polyvalent group or a polymer and n is at a number between 2 and 50, in particular between 2 and 10 and particularly preferably around 2 or 3. Furthermore, the composition according to the invention is characterized in that at least one of these two components A or B has more than two functionalities.

In order for fluorescence to be particularly intense after crosslinking, the group R _{1 should have} electron-donating properties. The electron-donating properties result from the sum of the resonance (R) and induction (I) effects. The important thing is that the sum of these two effects is electron-donating. Thus, a particularly preferred methoxy group has an -I effect. However, this is more than compensated by an opposite + R effect.

The group R ₂ is preferably ester or amide groups having a polyvalent radical R ₅ .

In a first preferred embodiment of the invention, this radical R ₅ is a di- or trivalent oligoether. Particularly preferred oligoethers are polyethylene oxide or polypropylene oxide.

With particular preference, component B in this first embodiment is a compound of the structure

Where m is a number between 2 and 10.

In a second, as it were preferred embodiment of the invention, the component B is a compound of the structure

erhalten. Dabei ist R₆ eine zweibindige Gruppe, bevorzugt eine Ethyliden- oder eine Propyliden-Gruppe. R₇ ist Wasserstoff oder eine Methylgruppe.In a third, as it were preferred embodiment of the invention, component B by copolymerization of (meth) acrylates and / or with (meth) acrylates copolymerizable monomers with a compound of the structure

receive. In this case, R _{6 is} a divalent group, preferably an ethylidene or a propylidene group. R ₇ is hydrogen or a methyl group.

In this third preferred embodiment, component A is preferably a poly (meth) acrylate having more than 2 vinyl groups. Equally suitable are vinyl-containing polymers which are compatible with the polymers of the component B used.

The notation (meth) acrylate in this context includes both acrylates and methacrylates, as well as mixtures of acrylates and methacrylates. Furthermore, these (meth) acrylates may additionally contain monomers which can be copolymerized with acrylates or methacrylates, for example styrene or itaconic acid. The same applies analogously to the formulation poly (meth) acrylates with respect to the corresponding polymerization products of these mixtures.

In other, in particular the previously described first two preferred embodiments, the component A is preferably a polymer having more than 2 vinyl groups. In particular, polyolefins which have vinyl groups are suitable as polymers. Particularly preferred examples of such polyolefins are EPDM, SBR, SBS, ABS, chloroprene rubber, poly-α-olefins, polyisoprene or polybutadiene. In these embodiments, component A is very particularly preferably a 1,2-polybutadiene or polybutadiene in the form of a copolymer having 1,2- and 1,4-linkages.

Regardless of the particular embodiment, the vinyl groups of component A and the functional groups of component B are preferably present in a molar ratio of at least 50 to 1 in the formulation. This ratio is particularly preferably between 100 to 1 and 1000 to 1, in particular between 200 to 1 and 500 to 1.

In addition to the formulations described, as it were a method for photo-induced crosslinking of this formulation of at least two different components A and B as described above, in which this formulation is activated by means of light, in particular UV or sunlight, preferably by means of sunlight and irreversibly crosslinked.

As an alternative to daylighting or sunlight curing, the activation can also be carried out selectively by irradiation with a UV light source at room temperature in this process. Particularly good results are achieved, for example, with UV light in the UVB range with a wavelength between 312 ± 5 nm. For example, a corresponding 36 W lamp is enough. The wavelength can also deviate from this value. Thus, for example, the reaction takes place only slightly slower with low-energy radiation.

An unexpected advantage of the present invention is that the degree of crosslinking after crosslinking can be determined by fluorescence measurements. In addition, it is possible to be able to adjust the degree of crosslinking initially by selecting the radiation intensity and the irradiation time. Under the influence of sunlight, it can then come later in the application to a further post-crosslinking.

In addition to the formulation and the method described, the use of these formulations according to the invention is also part of the present invention. The formulations described are particularly suitable for use in adhesives, sealants, molding compounds, coatings, inks or composite materials. A particular use in this case is the use as elastomeric shaped body, e.g. in children's toys dar.

Equally preferred are uses of the formulations according to the invention in security labels, luminous surfaces, rubber labels, light-conducting materials in the form of filaments, films or coatings or as fluorescent particles, which can be used as an additive.

Examples Precursor 1: 4 - ((2-tosylhydrazono) methyl) benzoic acid (1)

A mixture of 4-formyl-benzoic acid (6.558 g, 43.7 mmol, 1 equiv.) And p-toluenesulfonyl hydrazide (8.138 g, 43.7 mmol, 1 equiv.) In ethanol (100 mL) was refluxed for 30 min. The solution was diluted with water (100 mL) and the precipitate filtered off. The solid residue was washed with aqueous ethanol (100 mL). A yield of 14.5 g (98%) was obtained. The product was characterized by ¹ H-NMR (DMSO, 250 MHz).

Precursor 2: Preparation of the diazonium salt (2):

Anisidine (4 g, 32.5 mmol, 1 eq.) Was dissolved in a mixture of concentrated HCl (8.46 mL), H ₂ O (26.9 mL) and ethanol (26.9 mL) and brought to 0 ° C cooled. A cooled solution of sodium nitrite (2.241 g, 32.5 mmol, 1 equivalent) in water (13.45 mL) was added dropwise and stirred at 0 ° C for a further 10 min.

Precursor 3: Preparation of tetrazole (3):

The solution of the diazonium salt (2) was added dropwise over 45 minutes to a solution of the hydrazone (1) (10.34 g, 32.5 mmol, 1 equiv.) In pyridine (200 mL) at -10 ° C until. 5 ° C given. After completion of the addition, stirring was continued for 30 minutes at 0 ° C and allowed to thaw overnight at room temperature with stirring. The turbid mixture was poured into a 10% HCl solution (500 mL), the precipitate filtered off and washed with ethanol (250 mL). A yield of 6.2 g (65%) was obtained. The product was characterized by H-NMR (DMSO, 400 MHz).

Precursor 4: 4- (2- (4-methoxyphenyl) -2H-tetrazol-5-yl) benzoyl chloride (4):

The tetrazole (3) (1.00 g, 3.374 mmol, 1 equivalent) was suspended in dry tetrahydrofuran and thionyl chloride (4.01 g, 2.45 mL, 33.74 mmol, 10 equiv.) Was added under inert gas. The mixture was re-perfused for 4 hours and then all volatiles were removed under a slight vacuum. The residue was dissolved in tetrahydrofuran (20 mL) and dried in vacuo to drive off residual thionyl chloride. There was obtained 1.05 g (100%) yield. The characterization of the 1 product was carried out by means of H-NMR (DMSO, 400 MHz).

Precursor 5: Oxybis (ethane-2,1-diyl) bis (4- (2- (4-methoxyphenyl) -2H-tetrazol-5-yl) benzoate) (5):

The acid chloride (4) (1.06 g, 3.374 mmol, 5.0 equivalents) was dissolved in dry tetrahydrofuran (20 mL). A mixture of pyridine (134 mg, 136 μL, 1.69 mmol, 2.50 equiv.) And tetraethylene glycol (131 mg, 116 μL, 0.675 mmol, 1 equiv.) In dry tetrahydrofuran (20 mL) was added dropwise at room temperature and over Night stirred. The reaction was stopped by addition of water and the solvent was evaporated. The residue was suspended in dichloromethane (100 mL) and the insoluble starting material was filtered off. The filtrate was washed with 5% HCl and water, the organic phase dried with magnesium sulfate and then evaporated. The residue was taken up in a little chloroform and precipitated in ethanol. The yield was 120 mg (25%). The characterization of the 1 product was carried out by means of H-NMR (CDCl ₃ , 400 MHz).

Examples: Light-induced crosslinking reaction between 1,2-polybutadiene and the tetrazole crosslinker (5):

1,2-polybutadiene (JSR RB-820) and the crosslinker (5) (5% by weight based on the 1,2-polybutadiene) are mixed at 40 ° C in 5 mL tetrahydrofuran with shaking under dimmed laboratory light for one hour. After both components were completely dissolved, equal amounts of the mixture were aliquoted and placed in headspace vials (Pyrex, diameter 20 mm). The solvent was removed and fresh tetrahydrofuran (50 μL) added to each sample before being purged with nitrogen and sealed airtight with SBR seals with a PTFE inner layer. The samples were irradiated for the desired reaction time with constant rotation around a compact low pressure UV lamp (Philips TL01) with a distance of 40 to 50 mm. After illumination, 3 mL of tetrahydrofuran was added to the gel-like mixture and allowed to stand for 3 hours. The liquid components of the sample were decanted, the gel and the solution dried and weighed. The control samples were treated analogously, in which case no crosslinker was added. The experiments were repeated with different irradiation times. The gel fraction after irradiation for 30 min was 17% by weight (based on the initial weight of 1,2-polybutadiene and crosslinker (5)). After 1 h, the gel content was 20% by weight, after 2 hours 30% by weight and after 4 hours almost 60% by weight. After 20 h irradiation, finally, a gel content of about 80% by weight was achieved. The comparative samples of pure 1,2-polybutadiene were still completely soluble after 20 h.

The reaction was also carried out in the absence of solvents in a drawn film and under direct sunlight: in this case, only a portion (via a mask covering parts of the film) was exposed and crosslinked. The unexposed part could be removed again with solvents.

Claims (15)

Photo-induced crosslinkable formulation, characterized in that the formulation contains a component A which has at least two vinyl groups of the form CH 2 = CHR 3, wherein R 3 is a vinyl-containing polymer or oligomer, that the formulation contains a component B, the the structure

R ₁ is an amine group, a halogen or an ether group -OR ₄ with R ₄ selected from polyethers or linear or branched alkyl groups having 1 to 20 carbon atoms, R ₂ is a polyvalent group or a polymer and n is a number between 2 and 50, and that at least one of these two components A or B has more than two functionalities. A formulation according to claim 1, characterized in that it is a methoxy group, R ₂ is ester or amide groups with a multivalent radical R ₅ and n is 2 or R ₁ is. 3 Formulation according to at least one of claims 2, characterized in that R ₅ is a di- or trivalent oligoether. A formulation according to claim 3, characterized in that component B is a compound of the structure

where m is a number between 2 and 10. A formulation according to claim 1 or 2, characterized in that component B is a compound of the structure

is. A formulation according to claim 1 or 2, characterized in that the component B by copolymerization of (meth) acrylates and / or with (meth) acrylates copolymerizable monomers with a compound of the structure

wherein R ₆ is an ethylidene or a propylidene group and R ₇ is hydrogen or a methyl group. A formulation according to claim 6, characterized in that component A is more than 2 vinyl-containing poly (meth) acrylate. A formulation according to any one of claims 1 to 5, characterized in that component A is a polymer having more than 2 vinyl groups. A formulation according to claim 8, characterized in that component A is an EPDM, SBR, SBS, ABS, chloroprene rubber, a poly-α-olefin, a polyisoprene or a polybutadiene. A formulation according to claim 9, characterized in that component A is a 1,2-polybutadiene or polybutadiene in the form of a copolymer having 1,2- and 1,4-linkages. A formulation according to any one of claims 1 to 10, characterized in that the vinyl groups of component A and the functional groups of component B are present in a molar ratio of at least 50 to 1 in the formulation. A method of photoinduced crosslinking, characterized in that a formulation of at least two different components A and B according to any one of claims 1 to 11 is activated by means of light and irreversibly crosslinked. A method according to claim 12, characterized in that the activation takes place by means of irradiation with a UV light source at room temperature. Use of a formulation according to at least one of claims 1 to 11 in adhesives, sealants, molding compounds, coatings, inks, as an elastomeric molding or in composite materials. Use of a formulation according to at least one of claims 1 to 11 in security labels, luminous surfaces, rubber labels, light-conducting materials in the form of filaments, films or coatings or as fluorescent particles, which can be used as an additive.