Composition of photopolymerizable distribution-controlled block polymer as well as preparation method and application of composition

Abstract

The invention discloses a composition of a photopolymerizable distribution-controlled block polymer as well as a preparation method and application of the composition. The composition comprises a block polymer, an acrylate compound and a polymerization initiator, the block polymer comprises thermoplastic elastomer copolymers S1-C-S2 and / or (S-C) nX, S1, S2 and S are polyvinyl aromatic hydrocarbon blocks with the number-average molecular weight of 7000-40000, and C is a vinyl aromatic hydrocarbon-isoprene-butadiene random copolymer block. According to the composition, based on the synergistic effect of all the components, by regulating and controlling the content of all the block components and vinyl aromatic hydrocarbon in the block polymer, the excellent transparency and good processing hardness of the product are achieved at the same time, no extra production equipment needs to be added in the preparation process of the composition, and the composition has the advantages of being simple in process, wide in raw material source, low in cost and the like. The flexographic printing plate prepared on the basis of the composition has wear resistance, transparency and fine line reproducibility at the same time, and the application scene of the printing plate is greatly widened.

Description

Technical Field

[0001] The invention relates to a photopolymerizable composition, in particular to a photopolymerizable controlled distribution block polymer composition and a preparation method and application thereof, belonging to the technical field of flexible printing plates. Background Art

[0002] Photopolymerizable printing plates are used to prepare flexographic printing plates. Generally, the transparent image or text to be printed (other parts are opaque or less transparent) is placed under light radiation for photopolymerization. The area exposed to the light radiation undergoes photopolymerization, which makes it harder and less soluble than the unexposed area. Then, a suitable solvent is used to dissolve and rinse to remove the unexposed and unpolymerized areas while retaining the exposed areas, thereby obtaining a printing plate with the desired characteristics. Patents for obtaining printing plates by photopolymerization have long existed, such as CN100537263 C Method for manufacturing photopolymerizable lithographic printing plates, CN104339821A Method for manufacturing flexographic printing plate precursor for laser engraving, flexographic printing plate precursor for laser engraving, flexographic printing plate making method and flexographic printing plate, which describe in detail the method of preparing flexographic printing plates by laser irradiation photopolymerization. In addition, the preparation method of such photopolymerizable printing plates is mentioned in U.S. Patent Nos. 4266005, 4320188, 4126466, 4460675 and 5213948. Such printing plates generally include a carrier layer, an optional adhesive layer or other bottom layer, one or more photopolymerizable layers, an optional elastic intermediate layer and a cover layer.

[0003] The preparation of such a multi-layer photopolymerizable flexographic printing plate is usually carried out by calendering, that is, the composition is calendered between the carrier layer and the cover layer through a calender to form a photopolymerizable layer between the two layers. This method is fast and convenient.

[0004] Among the layers of the flexographic printing plate, the most technically demanding, researched and critical layer is the photopolymerizable layer. The photopolymerizable layer has a complex composition, containing adhesives, photopolymerizable monomers and polymers, photoinitiators and additional additives such as plasticizers, fillers and stabilizers.

[0005] The binder in the photopolymerizable layer is usually a thermoplastic elastic block polymer. These block polymers usually include a thermoplastic block A and an elastic block B, and their general formula is ABA or AB or (AB)n or (AB)nX, especially linear and star block polymers with polyvinyl aromatic ends, as described in CN1698015.

[0006] Such block polymers include the following block polymers or mixtures of the block polymers.

[0007] SBS Polystyrene-polybutadiene-polystyrene SIS Polystyrene-polyisoprene-polystyrene SI / BS Polystyrene-isoprene-butadiene copolymer-polystyrene (SB)nSi n(polystyrene-polybutadiene)silane, n is an integer of 1 to 4 (SI)nSi n(polystyrene-polyisoprene)silane, n is an integer of 1 to 4 (SI / B)nSi n(polystyrene-isoprene and butadiene copolymer)silane, n is an integer of 1 to 4

[0008] It is also known to use block polymers with a certain vinyl content in order to meet some special requirements, such as in EP 0 525 206 A, to improve the properties of printing plates with specific monomers, or to prepare printing plates without added monomers.

[0009] Until now, linear or star-shaped block polymers such as SBS and SIS or their mixtures have been mostly preferred for the manufacture of offset printing plates. This is because the raw materials of thermoplastic elastomers such as SBS and SIS are easily available, reasonably priced, and have excellent processability and transparency. However, these polymers have some disadvantages: for example, when SIS is used, the Shore hardness of the obtained offset printing plate is relatively low, and it is easy to degrade, causing the surface to become sticky and affecting its use; and when SBS is used to prepare offset printing plates, the processing stability is not satisfactory, and partial gel will be generated during the processing, resulting in poor resolution of the final developed plate.

[0010] Another method is to mix SBS and SIS to adjust the performance. The resulting printing plate has satisfactory flexibility and effectively improves the shortcomings of using either alone. However, by mixing, the two cannot achieve complete compatibility with each other, resulting in turbidity and UV scattering, which reduces resolution.

[0011] In order to solve the above problems, an improved photopolymerizable composition is used. The photopolymerizable composition includes a mixture of SIS and SBS block polymers as adhesives, ethylenically unsaturated monomers, plasticizers and photoinitiators. The SIS block polymer can be a conventional block polymer of styrene and isoprene (such as Baling's YH-1105, YH-1106 and KRATON○RD1161 and TSRC 1250, etc.). The improvement is that the vinyl content of the selected SBS block polymer is in the range of 50-60% (while the vinyl content of the general SBS block polymer is 10-20%). The use of such SBS can obtain a crystal-clear photopolymerizable composition, but the technicians in this field will be severely limited in the choice of the raw material SBS.

[0012] There is a further improved scheme, based on the binary copolymerization of vinyl aromatic hydrocarbon and isoprene or vinyl aromatic hydrocarbon and butadiene, a monomer is added, such as CN1698015 mentions a terpolymer SCS of vinyl aromatic hydrocarbon, isoprene and butadiene, wherein S is a vinyl aromatic hydrocarbon polymer block, and C is a random copolymer block (I / B) of isoprene and butadiene. This terpolymer overcomes the problem of UV scattering caused by the incompatibility of SIS and SBS.

[0013] However, the above solutions still have some shortcomings, such as chain scission and degradation of the middle block I / B or gelation during processing such as light irradiation. These problems lead to surface stickiness or poor resolution, which still bring a bad experience during use. The resulting flexible printed board cannot take into account the three major characteristics of defect resistance, excellent transparency and sufficient fine line reproducibility.

[0014] The present invention overcomes the problem of UV scattering caused by incomplete mutual compatibility between SIS and SBS, and is not limited in the choice of raw materials, while improving the problems of degradation and stickiness of the middle block and the generation of gel, so that the prepared flexible printed board has three major characteristics: defect resistance, excellent transparency and sufficient fine line reproducibility. Summary of the invention

[0015] In view of the problems existing in the prior art, the first object of the present invention is to provide a composition of a photopolymerizable controlled distribution block polymer. The composition is based on the synergistic effect between the components. By regulating the content of each block component and vinyl aromatic hydrocarbon in the block polymer, the product has excellent transparency and good processing hardness, solves the problem of UV scattering of the product caused by the incomplete compatibility of SIS and SBS, improves the problem of stickiness and gelation caused by degradation of the block polymer, thereby improving the versatility and compatibility of the product.

[0016] The second object of the present invention is to provide a method for preparing a composition of a photopolymerizable controlled distribution block polymer. The preparation process provided by the present invention is based on the production process of styrene block copolymers. By strictly adjusting the component parameters and polymerization steps of each block in each composition, the continuous preparation of the composition is achieved; the preparation process does not require the addition of additional production equipment, and has the advantages of simple process, wide source of raw materials, and low cost.

[0017] The third object of the present invention is to provide an application of a composition of a photopolymerizable controlled distribution block polymer for preparing a photopolymerizable flexographic printing plate. The flexographic printing plate prepared based on the composition provided by the present invention has excellent transparency and good processing hardness, improves the problems of stickiness and gelation caused by degradation of the block polymer, and enables the printing plate to have both damage resistance, transparency and fine line reproducibility, greatly broadening the application scenarios of the printing plate.

[0018] To achieve the above technical purpose, the present invention provides a composition of a photopolymerizable controlled distribution block polymer, comprising a block polymer, an acrylate compound and a polymerization initiator; the mass ratio of the block polymer to the acrylate compound is 0.3 to 98:1; the addition amount of the polymerization initiator is 0.5 to 10 wt% of the mass of the composition;

[0019] The block polymer comprises a thermoplastic elastomer copolymer, wherein the thermoplastic elastomer copolymer is S1-C-S2 and / or (SC)nX; wherein S1, S2 and S are polyvinyl aromatic hydrocarbon blocks each having a number average molecular weight of 7000 to 40000, C is a random copolymer block of vinyl aromatic hydrocarbon-isoprene-butadiene, n is an integer greater than or equal to 2, and X is a coupling agent residue; and the content of the polyvinyl aromatic hydrocarbon block in the thermoplastic elastomer copolymer is 10 to 45 wt%.

[0020] As a preferred solution, the composition further comprises a functional additive, and the added amount of the functional additive is not higher than 40% of the total mass of the composition.

[0021] As a preferred solution, the functional additive is at least one of a plasticizer, an antioxidant, an anti-polymerization inhibitor, a pigment and a rubber compatible with the composition.

[0022] As a preferred solution, the content of polyvinyl aromatic hydrocarbons in the thermoplastic elastomer copolymer is 15 to 35 wt %. More preferably, the content of polyvinyl aromatic hydrocarbons in the thermoplastic elastomer copolymer is 18 to 30 wt %.

[0023] As a preferred solution, the polyvinyl aromatic hydrocarbon is obtained by polymerization of at least one of styrene, C1-C4 alkyl styrene and C1-C4 dialkyl styrene. Further preferably, the polyvinyl aromatic hydrocarbon monomer is ethylene, α-methyl styrene, o-methyl styrene, p-methyl styrene, 1,3-dimethyl styrene, p-tert-butyl styrene, vinyl naphthalene or a mixture thereof.

[0024] As a preferred solution, the number average molecular weight of S1, S2 and S is 10000 to 25000. The number average molecular weight of S1, S2 and S must be strictly in accordance with the above requirements. The polyvinyl aromatic block in the block copolymer is an aggregate phase. If the aggregate phase is too large, it will cause scattering of light in certain bands, affecting transparency and resolution. If the aggregate phase is too small, the phase separation is incomplete or cannot be carried out. For flexible printed boards, the flexibility is poor, the clarity of the printed image is insufficient, and the printing durability is also poor.

[0025] As a preferred solution, the number of polymerization units contained in C is ≤50, wherein the content of vinyl aromatic units is 2-20wt%, and the mass ratio of isoprene units to butadiene units is 0.25-4:1. Further preferably, the number of monomer units contained in C is ≤20; the content of vinyl aromatic monomers in C is 3-10wt%. The number of monomers directly affects the chain length of C. If the number of monomers is too large, the chain length will be too long, which will cause light scattering and seriously affect the transparency of the product.

[0026] As a preferred solution, the block polymer further contains at least one of linear SBS, SIS and SI / BS and / or at least one of star-shaped SBS, SIS and SI / BS.

[0027] As a preferred solution, the mass proportion of S1-C-S2 and / or (SC)nX in the block polymer is ≥30%.

[0028] The block copolymer provided by the present invention can be a linear or branched star block copolymer, or a triblock, tetrablock or multiblock, but contains at least two polyvinyl aromatic blocks and one ternary random copolymer block C.

[0029] As a preferred solution, the acrylic ester compound contains at least one unsaturated olefinic bond; and the mass ratio of the block polymer to the acrylic ester compound is 1.8 to 19:1.

[0030] As a preferred solution, the acrylic acid ester compound is at least one of butyl acrylate, isodecyl acrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, trihydroxymethylpropane triacrylate and dipentaerythritol monohydroxy pentaacrylate.

[0031] As a preferred solution, the polymerization initiator is an organic substance containing a photoinitiator or a photoinitiator system, and the added amount of the polymerization initiator is 0.5 to 5 wt % of the mass of the composition.

[0032] As a preferred solution, the polymerization initiator is at least one of methyl benzoin, benzoin acetate, benzophenone, benzil dimethyl ketal and ethyl anthraquinone / 4,4-bis(dimethylamino)benzophenone.

[0033] The present invention also provides a preparation method of a composition of a photopolymerizable controlled distribution block polymer, comprising: uniformly mixing an inert solvent, a vinyl aromatic monomer, a regulator and an initiator to initiate polymerization of the vinyl aromatic, adding isoprene and butadiene after the polymerization is completed, mixing uniformly, adopting a starvation polymerization, adding the vinyl aromatic monomer again after the starvation polymerization is completed to carry out polymerization reaction or adding a coupling agent to carry out coupling reaction, adding a terminator at the end of the reaction, and obtaining a block polymer; alternatively, mixing an inert solvent, a vinyl aromatic monomer, a mixture of isoprene and butadiene, a regulator and an initiator to carry out polymerization reaction, adding the vinyl aromatic monomer again after the reaction is completed to carry out polymerization reaction, and obtaining a block polymer; uniformly mixing the block polymer and a functional additive and adding them to a preheated mixer, adding an acrylic ester compound and a polymerization initiator in sequence, mixing uniformly and cooling to room temperature, and obtaining the block polymer.

[0034] As a preferred solution, the solvent is at least one of cyclopentane, cyclohexane and n-hexane; and the terminator is one of methanol, ethanol, water, phenols and organic acids.

[0035] As a preferred solution, the regulator is at least one of N,N,N',N'-tetramethylethylenediamine, tetrahydrofuran, monoethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethoxyethane, 1,2-diethoxypropane and 1-ethoxy-2,2-tert-butoxyethane.

[0036] As a preferred solution, the coupling agent is a silicon coupling agent, an alkoxysilane, a tin coupling agent, a divinyl aromatic compound, a halogenated alkane and an epoxy compound.

[0037] As a preferred solution, the temperature of the preheated reactor is 120-150° C., the mixing method of the mixer is stirring mixing, the rotation speed is 30-60 rpm, and the stirring time is 4-5 min.

[0038] The present invention also provides an application of the composition of photopolymerizable controlled distribution block polymer, characterized in that it is used for preparing a photopolymerizable flexographic printing plate.

[0039] Compared with the prior art, the beneficial technical effects of the present invention are:

[0040] 1) The composition provided by the present invention is based on the synergistic effect between the components. By regulating the content of each block component and vinyl aromatic hydrocarbon in the block polymer, the product has excellent transparency and good processing hardness, and solves the problem of UV scattering of the product caused by the incomplete compatibility of SIS and SBS, and improves the problem of stickiness and gelation caused by the degradation of the block polymer, thereby improving the versatility and compatibility of the product.

[0041] 2) The preparation process provided by the present invention is based on the production process of styrene block copolymers. By strictly adjusting the component parameters and polymerization steps of each block in each composition, the continuous preparation of the composition is achieved; the preparation process does not require the addition of additional production equipment and has the advantages of simple process, wide source of raw materials, and low cost.

[0042] 3) In the technical solution provided by the present invention, the flexible printing plate prepared based on the composition provided by the present invention has excellent transparency and good processing hardness, improves the problems of stickiness and gelation caused by the degradation of block polymers, so that the printing plate has both damage resistance, transparency and fine line reproducibility, greatly broadening the application scenarios of the printing plate. DETAILED DESCRIPTION

[0043] The present invention is specifically described by the following examples, but the scope of the present invention is not limited to these embodiments.

[0044] The preparation processes of the embodiments and comparative examples provided by the present invention are all prepared according to the following steps:

[0045] A 5 L stainless steel polymerization reactor with a jacket and agitator was heated with N 2 After full replacement, 3000ml of cyclohexane, 0.4g of tetrahydrofuran, 1.6g of N,N,N',N'-tetramethylethylenediamine, and 37.5g of styrene were added, and warm water was passed through the jacket. The materials in the polymerization kettle were heated to about 55°C while stirring, and n-butyl lithium cyclohexane solution (0.17g of pure n-butyl lithium) was added to start the first stage of styrene polymerization. After styrene was completely polymerized, the second stage of random polymerization was started: 21g of styrene was mixed evenly with 102g of isoprene and 102g of butadiene in a metering tank, and the temperature in the polymerization kettle was kept above 70°C. The mixture was continuously and evenly added to the polymerization kettle, and the feeding time was kept above 60min. After the addition of the mixture was completed for 2min, 37.5g of styrene was added to carry out the third stage of polymerization. After the reaction of styrene was completed, 0.1g of methanol was added to terminate the reaction, and a block polymer was obtained. 1 g of primary antioxidant 1076 and 1 g of secondary antioxidant 168 were added to the obtained block polymer, the solvent was removed by steam condensation, and the mixture was dehydrated and dried using a hot roller to obtain a linear block polymer SSIBS sample.

[0046] The polymerization process of the first stage of styrene polymerization is the same as that of the second random stage, but the difference in the material ratio of the first stage is that the amount of styrene and n-butyl lithium added is different. The amount of styrene in the first stage is 75g, and the amount of pure n-butyl lithium is 0.33g. The material ratio of the second stage is the same, and silicon tetrachloride cyclohexane solution is added as a coupling agent in the third stage (converted to pure silicon tetrachloride 0.17g). The coupling reaction is carried out for 20min to obtain a star-shaped block polymer (SSIB)nSi.

[0047] In addition, those skilled in the art know that by changing the feed amount of each segment and the monomer or the ratio of each monomer in the middle block and the amount of initiator, or adding a suitable coupling agent in the third segment, thermoplastic elastomer samples with different molecular weights and different structures can be obtained as shown in Table 2 below.

[0048] The components in the examples are described in Tables 2 and 3. The substances in the tables are only examples, but are not limited to the following substances.

[0049] Table 2 Various thermoplastic elastomers

[0050]

[0051] * represents the sum of the wt% of the vinyl aromatic content in the two end polyvinyl aromatic blocks / wt% of the vinyl aromatic content in the middle ternary random copolymer block.

[0052] I / B represents a random copolymer block of isoprene and butadiene. Similarly, S / I / B represents a random copolymer block of vinyl aromatic hydrocarbon, isoprene and butadiene.

[0053] Table 3 Auxiliary additives

[0054] Mineral plasticizers <![CDATA[ONDINA TM N68 fully hydrogenated naphthenic mineral oil]]> Photoinitiator 2,2-Dimethoxy-1,2-diphenylethan-1-one Antioxidants β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

[0055] Mixing process

[0056] The proportions of each component in the mixing process are all weight ratios. The plasticizer and solid rubber are mixed at room temperature, and the weight ratio of plasticizer: solid rubber is 1:5. The mixture is poured into a mixer rotating at 50 rpm and preheated at 140°C. Then, the acrylate compound is added into the mixer, and the acrylate compound: solid rubber is 1:10. After adding all the previous ingredients, the reaction monomer is added, mixed for 4-5 minutes, and then the photoinitiator is added. The amount of the photoinitiator added is 2% of the sum of the weight of the solid rubber and the acrylate compound, and mixed quickly. After mixing, take out the mixture and cool it to room temperature for use.

[0057] Plate making process

[0058] The mixture was sandwiched between a polyester film support coated with a thermoplastic elastomer adhesive and having a thickness of 125 μm and a polyester cover sheet having a 4 μm polyamide layer and a thickness of 100 μm, and a 2.5 mm spacer was used to press at 130°C and 200 kg / cm 2 The pressurization was performed for 4 minutes to obtain a photosensitive structure for a flexible printing plate.

[0059] The cover sheet of the photosensitive structure was removed, and the negative film was placed on the polyamide protective layer on the photopolymerizable composition layer for the flexible printed plate. The negative film was exposed to light at 240 mJ / cm2 from the support side using an ultraviolet fluorescent lamp with a central wavelength of 370 nm on an AFT-1500 exposure machine (ASAHI KASEI E-materials Corp.). 2 The whole surface is exposed. Then 8000mJ / cm 2 image exposure.

[0060] The plate was attached to the rotating drum of an AFP-1500 developer (Asahi-Kasei Chemicals Corporation) with adhesive, developed in a 3-methoxybutyl acetate developer at 25° C. for 5 min, and then dried at 60° C. for 2 hours.

[0061] Use a small UV radiation meter (such as UV Process Supply Inc.) to detect the UV dosage of the following curing process.

[0062] Use a germicidal lamp with a central wavelength of 254nm to irradiate the entire surface of the plate with 1000mJ / cm 2 After exposure, use ultraviolet fluorescent lamp to 1000mJ / cm 2 After post-exposure, the desired flexible printed board is obtained.

[0063] About the test

[0064] (1H-NMR) nuclear magnetic resonance can be used to determine the vinyl aromatic content in the vinyl aromatic block and the ternary random copolymer block.

[0065] Haze: Haze was measured on Colorquest II according to ASTM D1003 and is expressed as scattering % (Tr%) in the table.

[0066] Reflectivity: Using "THE ColorQUEST", at reflectance 45 / 0Observer 2 0 Reflectivity measured in mode (incident angle = 45 0 , observing the reflectivity perpendicular to the panel). The standard black panel has a reflectivity of 0%.

[0067] UV transmittance: The board on the UV small irradiator passes under the UV lamp, and the ratio of UV intensity with and without the board is the transmittance. The board thickness is 2mm.

[0068] Gel content: Weigh the measured plate and soak it in a large amount of toluene overnight, filter out the undissolved part, and dry it at 70°C in a vacuum until the weight does not drop further. Gel content (%) = W 干燥 / W 起始 *100, where W 干燥 W is the weight of the undissolved part after being immersed in toluene overnight and then dried. 起始 is the weight of the measured plate before immersion in toluene.

[0069] Defect resistance: A negative film with 8-12 point text was used to prepare a flexible printed board. The text damage degree after rubbing about 300 times was observed using an NP type brush force tester (the contact body was cloth, the size was 8cmX6cm, and the load was 1kg) and a microscope.

[0070] Regarding light transmittance, it is expressed as reflectivity at 400nm. The lower the reflectivity, the higher the light transmittance. The test data is shown in Table 4.

[0071] Table 4

[0072] SIS / SBS ​​weight ratio (wt%) Reflectivity at 400nm (%) 100 / 0 2.9 90 / 10 3.9 80 / 20 3.7 70 / 30 4.5 60 / 40 7.3 40 / 60 6.6 30 / 70 5.7 20 / 80 3.8 10 / 90 2.7 0 / 100 1.6 Blanco Whitening Agent 0.0

[0073] From the data in Table 4, it can be seen that the reflectivity of pure SIS or SBS at 400nm is 2.9% and 1.6% respectively. Such reflectivity indicates that the transparency of the offset printing plate made of the pure components of the two is quite excellent.

[0074] However, the disadvantage is that, for the mixture of the above two, except for SIS / SBS=10 / 90 with a reflectivity of 2.7%, the other mixtures have low transmittance and high reflectivity (higher than 3%), especially in the range of 20 / 80-80 / 20, and more obviously in the range of 30 / 70-70 / 30, the reflectivity is higher. At a ratio of about 50 / 50, the reflectivity shows a maximum value. The reflectivity in the range of 20 / 80-80 / 20 is equivalent to a white "milky" turbidity in the sample. Therefore, users can only use almost pure SIS or SBS polymers to prepare low-scattering and high-transparency adhesives or flexible offset printing plates, and cannot use such SIS and SBS to formulate an acceptable intermediate formula with high transmittance / low reflectivity. However, the intermediate formula can provide the formulator with much more flexibility to adjust the properties of SIS and SBS, so the intermediate formula is necessary and essential.

[0075] The data in Table 5 show that by combining the properties of SIS and SBS polymers, technicians can improve certain deficiencies of individual SIS or SBS polymers, such as improving the degradation of SIS (increase in MFR) and the problem of gelation caused by SBS cross-linking during processing (processing temperature is typically 140°C to 180°C) while maintaining excellent transparency.

[0076] In Table 5, MFR (4 min) and MFR (16 min) respectively represent the melt flow index measured after heating at 160° C. for 4 min and 16 min.

[0077] Table 5

[0078]

[0079] The compositions of the rubber sheets of the printing plates in the examples and comparative examples obtained from the above different thermoplastic elastomers are shown in Table 6, which also provides the transparency of the obtained printing plates.

[0080] Table 6 Transparency of the printing plates obtained in Examples 1 to 10 and Comparative Examples 1 to 6

[0081]

[0082]

[0083] *The data respectively represent the vinyl content in each component of the corresponding rubber components in the second column of the table.

[0084] Example 1 A linear S(S / I / B)S was prepared according to the above-mentioned method for preparing a block polymer, and then a flexible printed board was obtained by using the above-mentioned mixing process and plate making process, and then various tests were carried out.

[0085] The preparation methods of the block polymers in the remaining embodiments and comparative examples are basically the same as the preparation methods of the aforementioned block polymers. The linear structure is the same as the linear S(S / I / B)S, and the star structure is the same as the star (S(S / I / B))nSi. The difference lies in the material ratio and the monomer type of the second stage.

[0086] The mixing process and plate making process used in the other embodiments and comparative examples are exactly the same. The difference lies in the types and proportions of the solid rubber used. The specific types and proportions are shown in Table 6.

[0087] From the data in Table 6, it can be seen that the SBS+SIS mixture has a high scattering rate and a low transmittance, indicating that its transparency is too poor to be used for printing plates.

[0088] By comparing the data of the three samples with **, it can be directly observed that S(S / I / B)S and (S(S / I / B))nX have a very obvious compatibilizing effect on SIS and SBS. Although the UV transmittance is barely acceptable, it is close to the boundary value. Such data show that at least 30% of S(S / I / B)S or (S(S / I / B))nX is required in the mixture to be used for printing plates with lower clarity requirements. If the clarity requirement is higher, the amount of the block polymer of the present invention must be increased.

[0089] Examples 9 and 10 demonstrate that liquid SI and PB can be mixed with the block polymer of the present invention to obtain a mixed system with good transparency.

[0090] The defect resistance test results are shown in Table 7. If the text is not damaged, it is indicated by "O", and if the text is damaged, it is indicated by "X".

[0091] Table 7 Defect resistance test results of the printing plates obtained in Examples 1 to 10 and Comparative Examples 1 to 6

[0092] Rubber sheet composition Defectiveness test results for 5 times Comparative Example 1 SIS O OOO X Comparative Example 2 SBS O OXXX Comparative Example 3 SIBS O OOO X Comparative Example 4 SIBS O OOO X Comparative Example 5 SIS+SBS; 50 / 50 OOOXX Comparative Example 6 (SI)n O OOO X Comparative Example 7 (SB)nX O OXXX Comparative Example 8 (SIB)nX OOOXX Example 1 S(S / I / B)S OOOOO Example 2 S(S / I / B)S OOOOO Example 3 (S(S / I / B))nX OOOOO Example 4 (S(S / I / B))nX OOOOO Example 5 S(S / I / B)S+SIS; 50 / 50 OOOOO Example 6 S(S / I / B)S+SBS; 50 / 50 O OOO X Example 7 S(S / I / B)S+SIS+SBS; 33 / 33 / 33 O OOO X Example 8 (S(S / I / B))nX+SIS+SBS; 33 / 33 / 33 O OOO X Example 9 (S(S / I / B))nX+Liquid SI; 85 / 15 OOOOO Example 10 (S(S / I / B))nX+Liquid PB; 85 / 15 OOOOO

[0093] From the test results in Table 7, it can be seen that the photopolymerizable composition comprising the controlled distribution block polymer of the present invention shows great advantages in terms of the defect resistance of the prepared offset printing plate.

Claims

1. A composition of a photopolymerizable controlled distribution block polymer, characterized in that: It comprises a block polymer, an acrylate compound and a polymerization initiator; the mass ratio of the block polymer to the acrylate compound is 0.3 to 98:1; the addition amount of the polymerization initiator is 0.5 to 10 wt% of the mass of the composition; The block polymer comprises a thermoplastic elastomer copolymer, wherein the thermoplastic elastomer copolymer is S1-C-S2 and / or (SC)nX; wherein S1, S2 and S are polyvinyl aromatic hydrocarbon blocks each having a number average molecular weight of 7000 to 40000, C is a random copolymer block of vinyl aromatic hydrocarbon-isoprene-butadiene, n is an integer greater than or equal to 2, and X is a coupling agent residue; and the content of the polyvinyl aromatic hydrocarbon block in the thermoplastic elastomer copolymer is 10 to 45 wt%.

2. The composition of a photopolymerizable controlled distribution block polymer according to claim 1, characterized in that: The composition further comprises a functional additive, the addition amount of which is not higher than 40% of the total mass of the composition; the functional additive is at least one of a plasticizer, an antioxidant, an anti-polymerization inhibitor, a pigment and a rubber compatible with the composition.

3. The composition of a photopolymerizable controlled distribution block polymer according to claim 1, characterized in that: The content of polyvinyl aromatic hydrocarbon in the thermoplastic elastomer copolymer is 15-35 wt %; the polyvinyl aromatic hydrocarbon is obtained by polymerizing at least one of styrene, C1-C4 alkyl styrene and C1-C4 dialkyl styrene.

4. The composition of a photopolymerizable controlled distribution block polymer according to claim 1, characterized in that: The number average molecular weight of S1, S2 and S is 10000-25000; the number of polymerization units contained in C is ≤50, wherein the content of vinyl aromatic units is 2-20wt%, and the mass ratio of isoprene units to butadiene units is 0.25-4:

1.

5. The composition of a photopolymerizable controlled distribution block polymer according to claim 1, characterized in that: The block polymer further contains at least one of linear SBS, SIS and SI / BS and / or at least one of star-shaped SBS, SIS and SI / BS; the mass proportion of S1-C-S2 and / or (SC)nX in the block polymer is ≥30%.

6. The photopolymerizable controlled distribution block polymer composition according to claim 1, characterized in that: The acrylic acid ester compound contains at least one unsaturated olefinic bond; the mass ratio of the block polymer to the acrylic acid ester compound is 1.8 to 19:

1.

7. A photopolymerizable controlled distribution block polymer composition according to claim 6, characterized in that: The acrylic acid ester compound is at least one of butyl acrylate, isodecyl acrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, trihydroxymethylpropane triacrylate and dipentaerythritol monohydroxy pentaacrylate.

8. The photopolymerizable controlled distribution block polymer composition according to claim 1, characterized in that: The polymerization initiator is an organic substance containing a photoinitiator or a photoinitiator system, and the addition amount of the polymerization initiator is 0.5-5wt% of the mass of the composition.

9. The photopolymerizable controlled distribution block polymer composition according to claim 8, characterized in that: The polymerization initiator is at least one of methyl benzoin, benzoin acetate, benzophenone, benzil dimethyl ketal and ethyl anthraquinone / 4,4-bis(dimethylamino)benzophenone.

10. A method for preparing a photopolymerizable controlled distribution block polymer composition according to any one of claims 1 to 9, characterized in that: An inert solvent, vinyl aromatic monomer, regulator and initiator are mixed evenly to initiate polymerization of vinyl aromatic. After the polymerization is completed, isoprene and butadiene are added and mixed evenly, and polymerization is carried out by starvation method. After the starvation method polymerization is completed, vinyl aromatic monomer is added again for polymerization reaction or coupling agent is added for coupling reaction. When the reaction is completed, a terminator is added to obtain a block polymer. Alternatively, an inert solvent, vinyl aromatic monomer, a mixture of isoprene and butadiene, a regulator and an initiator are mixed for polymerization reaction. When the reaction is completed, vinyl aromatic monomer is added again for polymerization reaction to obtain a block polymer. After the block polymer and the functional additive are mixed evenly, they are added to a preheated mixer, and an acrylic ester compound and a polymerization initiator are added in sequence. After mixing evenly, the mixture is cooled to room temperature to obtain the block polymer.

11. The method for preparing a photopolymerizable controlled distribution block polymer composition according to claim 10, characterized in that: The solvent is at least one of cyclopentane, cyclohexane and n-hexane; the terminator is one of methanol, ethanol, water, phenols and organic acids; the regulator is at least one of N,N,N',N'-tetramethylethylenediamine, tetrahydrofuran, monoethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethoxyethane, 1,2-diethoxypropane and 1-ethoxy-2,2-tert-butoxyethane; the coupling agent is a silicon coupling agent, an alkoxysilane, a tin coupling agent, a divinyl aromatic compound, a halogenated alkane and an epoxy compound.

12. The method for preparing a photopolymerizable controlled distribution block polymer composition according to claim 10, characterized in that: The temperature of the preheated reactor is 120-150° C., the mixing method of the mixer is stirring mixing, the rotation speed is 30-60 rpm, and the stirring time is 4-5 minutes.

13. Use of a photopolymerizable controlled distribution block polymer composition according to any one of claims 1 to 9, characterized in that: Used to prepare photopolymerizable flexographic printing plates.

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