A composition of a photopolymerizable controlled distribution block polymer and a method of making and using the same

Abstract

The application discloses a kind of photopolymerizable controlled distribution block polymer composition and its preparation method and application.The composition includes block polymer, acrylate compound and polymerization initiator;The block polymer includes thermoplastic elastomer copolymer S1-C-S2 and / or (S-C) nX, S1, S2 and S are polyvinyl aromatic block with number average molecular weight of 7000~40000, C is vinyl aromatic-isoprene-butadiene random copolymer block.The composition is based on the synergistic effect between components, by regulating the block component in block polymer and vinyl aromatic content, while realizing the excellent transparency and good processing hardness of product, the preparation process of the combination does not need to add additional production equipment, with the advantages of simple process, raw material source is extensive, cost is low etc.Based on the composition prepared flexible printing plate is simultaneously provided with damage resistance, transparency and fine line reproducibility, and greatly widens the application scene of printing plate.

Description

Technical Field

[0001] This invention relates to a photopolymerizable composition, specifically to a photopolymerizable composition of a controlled-distribution block polymer, its preparation method, and its application, belonging to the field of flexible printing plate technology. Background Technology

[0002] Photopolymerizable printing plates are used to prepare flexographic printing plates. Generally, the transparent image or text to be printed (with other parts opaque or poorly transparent) is placed under light radiation for photopolymerization. The areas exposed to the light radiation undergo photopolymerization, resulting in them being harder and less soluble than the unexposed areas. Then, a suitable solvent is used to dissolve and rinse away the unexposed, unpolymerized areas while retaining the exposed areas, thus obtaining a printing plate with the desired characteristics. Patents for obtaining printing plates through photopolymerization have existed for some time, such as CN100537263 C, "Method for Manufacturing Photopolymerizable Lithographic Printing Plate," and CN104339821A, "Method for Manufacturing a Flexographic Printing Plate Master for Laser Engraving," "Flexographic Printing Plate Master for Laser Engraving," "Flexographic Printing Plate Making Method," and "Flexographic Printing Plate," which detail methods for preparing flexographic printing plates using laser irradiation photopolymerization. Furthermore, U.S. patents No. 4266005, No. 4320188, No. 4126466, No. 4460675, and No. 5213948 all mention methods for preparing photopolymerizable printing plates. Such printing plates typically include a carrier layer, an optional adhesive layer or other underlayer, one or more photopolymerizable layers, an optional elastic intermediate layer, and a capping layer.

[0003] The preparation of such multilayer photopolymerizable flexible printing plates is usually carried out by calendering, which involves calendering the composition between the carrier layer and the cover layer using a calendering machine, thereby forming a photopolymerizable layer between the two layers. This method is fast and convenient.

[0004] Among the layers of a flexographic printing plate, the most technologically advanced, extensively researched, and crucial layer is the photopolymerizable layer. The photopolymerizable layer has a complex composition, containing binders, photopolymerizable monomers and polymers, photoinitiators, and additional additives such as plasticizers, fillers, and stabilizers.

[0005] The binder in the photopolymerizable layer is typically a thermoplastic elastic block polymer. These block polymers generally include thermoplastic blocks A and elastic blocks B, with general formulas such as ABA, AB, (AB)n, or (AB)nX, especially linear and star-shaped block polymers with polyvinyl aromatic ends, as described in CN1698015.

[0006] This block polymer includes the block polymers described below or mixtures of said block polymers.

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

[0008] It is also known to use block polymers with a certain vinyl content to meet some special requirements, such as in EP0525206A to improve the performance of printing plates with special monomers, or to prepare printing plates without added monomers.

[0009] To date, linear or star-shaped block polymers such as SBS and SIS, or mixtures thereof, are generally preferred for manufacturing printing plates. This is because thermoplastic elastomers like SBS and SIS are readily available, reasonably priced, and possess excellent processability and transparency. However, these polymers have some drawbacks: for example, using SIS results in printing plates with lower Shore hardness and a tendency to degrade, causing a sticky surface and affecting usability; while using SBS to prepare printing plates results in unsatisfactory processing stability, leading to partial gelation during processing and ultimately poor resolution in the final developing plate.

[0010] Another approach is to mix SBS and SIS to adjust performance, resulting in printed circuit boards with satisfactory flexibility and effectively improving the shortcomings of using either alone. However, by mixing, the two cannot achieve complete compatibility, leading to clouding and UV scattering, which reduces resolution.

[0011] To address the aforementioned problems, improved photopolymerizable compositions have been developed. These compositions comprise a mixture of SIS and SBS block polymers as a binder, olefinically unsaturated monomers, a plasticizer, and a photoinitiator. The SIS block polymer can be a conventional styrene-isoprene block polymer (such as Baling's YH-1105, YH-1106, KRATON ORRD1161, and TSRC 1250). The improvement lies in the vinyl content of the selected SBS block polymer, which is in the range of 50-60% (while typical SBS block polymers have a vinyl content of 10-20%). Using such SBS yields a crystal-clear photopolymerizable composition, but this severely limits the selection of the raw material SBS for those skilled in the art.

[0012] Further improvements are possible by adding a monomer to the binary copolymerization of vinyl aromatics with isoprene or vinyl aromatics with butadiene. For example, CN1698015 mentions a terpolymer SCS of vinyl aromatics, isoprene, and butadiene, where S is the ethylene aromatics polymer block and C is the 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 aforementioned solutions still have some shortcomings. For example, the intermediate block I / B may undergo chain scission degradation or gel formation during processing such as light irradiation. These problems can lead to surface stickiness or poor resolution, resulting in a poor user experience. Consequently, the resulting flexible printed circuit board cannot simultaneously achieve the three major characteristics of damage resistance, excellent transparency, and high fine line reproducibility.

[0014] This invention overcomes the problem of UV scattering caused by the incomplete compatibility of SIS and SBS, and is not limited in the selection of raw materials. It also improves the problems of degradation and stickiness of the intermediate block and gel formation. The resulting flexible printed circuit board possesses three major characteristics: damage resistance, excellent transparency, and excellent fine line reproducibility. Summary of the Invention

[0015] To address the problems existing in the prior art, the first objective of this invention is to provide a composition of controllably distributed block polymers that can be photopolymerized. This composition, based on the synergistic effect between its components, achieves excellent transparency and good processing hardness by controlling the content of each block component and vinyl aromatic hydrocarbon in the block polymer. It also solves the problem of UV scattering caused by the incomplete incompatibility of SIS and SBS, and improves the problems of stickiness and gel formation due to the degradation of block polymers, thereby improving the versatility and compatibility of the product.

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

[0017] A third objective of this invention is to provide an application of a composition of photopolymerizable controlled-distribution block polymers for the preparation of photopolymerizable flexible printing plates. Flexible printing plates prepared based on the compositions provided by this invention exhibit excellent transparency and good processing hardness, improving upon the problems of stickiness and gel formation caused by block polymer degradation. This allows the printing plates to simultaneously possess durability, transparency, and fine line reproducibility, significantly expanding the application scenarios of printing plates.

[0018] To achieve the above-mentioned technical objectives, the present invention provides a composition of a controllably distributed block polymer that can be photopolymerized, comprising a block polymer, an acrylate compound, and a polymerization initiator; wherein the mass ratio of the block polymer to the acrylate compound is 0.3 to 98:1; and the amount of the polymerization initiator added is 0.5 to 10 wt% of the composition mass.

[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 blocks with a number average molecular weight of 7000 to 40000, C is a vinyl aromatic-isoprene-butadiene random copolymer block, n is an integer greater than or equal to 2, and X is a coupling agent residue; the content of the polyvinyl aromatic block in the thermoplastic elastomer copolymer is 10 to 45 wt%.

[0020] As a preferred embodiment, the composition further includes functional additives, wherein the amount of functional additives added does not exceed 40% of the total mass of the composition.

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

[0022] As a preferred embodiment, the polyvinyl aromatic hydrocarbon content in the thermoplastic elastomer copolymer is 15-35 wt%. More preferably, the polyvinyl aromatic hydrocarbon content in the thermoplastic elastomer copolymer is 18-30 wt%.

[0023] As a preferred embodiment, the polyvinyl aromatic hydrocarbon is obtained by polymerization of at least one selected from styrene, C1-C4 alkylstyrene, and C1-C4 dialkylstyrene. More preferably, the polyvinyl aromatic hydrocarbon monomer is ethylene, α-methylstyrene, o-methylstyrene, p-methylstyrene, 1,3-dimethylstyrene, p-tert-butylstyrene, vinylnaphthalene, or mixtures thereof.

[0024] As a preferred embodiment, the number average molecular weights of S1, S2, and S are 10,000 to 25,000. The number average molecular weights of S1, S2, and S must strictly adhere to the above requirements. In block copolymers, the polyvinyl aromatic blocks are aggregated phases. If the aggregated phase is too large, it will cause scattering of light in certain wavelengths, affecting transparency and resolution. If the aggregated phase is too small, phase separation will be incomplete or impossible. When used in flexible printing plates, this results in poor flexibility, insufficient clarity of printed images, and poor printability.

[0025] As a preferred embodiment, the number of polymeric units contained in C is ≤50, wherein the content of vinyl aromatic units is 2-20 wt%, and the mass ratio of isoprene units to butadiene units is 0.25-4:1. More preferably, the number of monomeric units contained in C is ≤20; and the content of vinyl aromatic monomers in C is 3-10 wt%. The number of monomers directly affects the chain length of C. If the number of monomers is too high, the chain length will be too long, leading to light scattering and severely affecting the transparency of the product.

[0026] As a preferred embodiment, 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 embodiment, the block polymer contains ≥30% by mass of S1-C-S2 and / or (SC)nX.

[0028] The block copolymers provided by this invention can be linear or branched star-shaped block copolymers. They can also be triblock, tetrablock, or multiblock copolymers, but they contain at least two polyvinyl aromatic blocks and one ternary random copolymer block C.

[0029] As a preferred embodiment, the acrylate compound contains at least one unsaturated olefin bond; the mass ratio of the block polymer to the acrylate compound is 1.8 to 19:1.

[0030] As a preferred embodiment, the acrylate compound is at least one selected from butyl acrylate, isodecanyl acrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, and dipentaerythritol monohydroxypentaacrylate.

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

[0032] As a preferred embodiment, the polymerization initiator is at least one selected from methylbenzoin, benzoin acetate, benzophenone, benzoyl dimethyl ketal, and ethyl anthraquinone / 4,4-bis(dimethylamino)benzophenone.

[0033] This invention also provides a method for preparing a composition of a photopolymerizable controlled-distribution block polymer. The method involves uniformly mixing an inert solvent, vinyl aromatic monomers, a regulator, and an initiator to initiate vinyl aromatic polymerization. After polymerization is complete, isoprene and butadiene are added and mixed uniformly. A starvation polymerization process is then employed. After the starvation polymerization is complete, vinyl aromatic monomers are added again for polymerization, or a coupling agent is added for coupling. A terminator is added at the end of the reaction to obtain the block polymer. Alternatively, an inert solvent, vinyl aromatic monomers, a mixture of isoprene and butadiene, a regulator, and an initiator are mixed and polymerized. After the reaction is complete, vinyl aromatic monomers are added again for polymerization to obtain the block polymer. The block polymer and functional additives are then uniformly mixed and added to a preheated mixer. An acrylate compound and a polymerization initiator are added sequentially, and after uniform mixing, the mixture is cooled to room temperature to obtain the final product.

[0034] As a preferred embodiment, the solvent is at least one selected from cyclopentane, cyclohexane, and n-hexane; the terminating agent is one selected from methanol, ethanol, water, phenols, and organic acids.

[0035] As a preferred embodiment, the regulator is at least one selected from 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 embodiment, the coupling agent is a silicon coupling agent, an alkoxysilane, a tin coupling agent, a divinyl aromatic compound, a haloalkane, or an epoxy compound.

[0037] As a preferred embodiment, the preheated reactor temperature is 120–150°C, the mixer uses stirring to mix, the speed is 30–60 rpm, and the stirring time is 4–5 min.

[0038] The present invention also provides an application of a composition of photopolymerizable controlled-distribution block polymers, characterized in that it is used to prepare photopolymerizable flexible printing plates.

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

[0040] 1) The composition provided by the present invention achieves excellent transparency and good processing hardness of the product by controlling the content of each block component and vinyl aromatic hydrocarbon in the block polymer based on the synergistic effect between the components. It also solves the problem of UV scattering caused by the incompatibility between SIS and SBS, and improves the problem of stickiness and gel formation caused by the degradation of block polymer, thereby improving the versatility and compatibility of the product.

[0041] 2) The preparation process provided by this 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. This preparation process does not require the addition of additional production equipment and has the advantages of simple process, wide availability 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, which improves the problem 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 expanding the application scenarios of the printing plate. Detailed Implementation

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

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

[0045] A 5L stainless steel polymerization reactor equipped with a jacket and stirrer was fully purged with nitrogen (N2). 3000ml of cyclohexane, 0.4g of tetrahydrofuran, 1.6g of N,N,N',N'-tetramethylethylenediamine, and 37.5g of styrene were added. Warm water was circulated into the jacket. The material in the polymerization reactor was stirred while the temperature was raised to approximately 55°C. A solution of n-butyllithium cyclohexane (0.17g of pure n-butyllithium) was added to begin the first stage of styrene polymerization. After the styrene had 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 vessel. The temperature inside the polymerization reactor was maintained above 70°C. The mixture was continuously and evenly added to the polymerization reactor, maintaining the feeding time at least 60 minutes. Two minutes after the mixture was completely added, another 37.5g of styrene was added to initiate the third stage of polymerization. After the styrene reaction was complete, 0.1g of methanol was added to terminate the polymerization, yielding a block polymer. The obtained block polymer was mixed with 1g of primary antioxidant 1076 and 1g of secondary antioxidant 168. The solvent was removed by steam condensation and the polymer was dehydrated and dried using a hot roller to obtain a linear block polymer SSIBS sample.

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

[0047] Furthermore, those skilled in the art will know that by changing the amount of material added to each segment and the ratio of monomers or monomers in the intermediate block and the amount of initiator, or by adding a suitable coupling agent to the third segment, thermoplastic elastomer samples with different molecular weights and structures, as shown in Table 2 below, can be obtained.

[0048] The components described in the examples are shown in Tables 2 and 3 below. The substances in each table are for illustrative purposes only and are not limited to the substances listed below.

[0049] Table 2 Various thermoplastic elastomers

[0050]

[0051] * indicates the sum of vinyl aromatic hydrocarbon contents (wt%) in the polyvinyl aromatic hydrocarbon blocks at both ends / the vinyl aromatic hydrocarbon content (wt%) 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 aromatics with isoprene and butadiene.

[0053] Table 3. Additives

[0054] Mineral plasticizers <![CDATA[ONDINA TM N68 fully hydrogenated naphthenic mineral oil Photoinitiator 2,2-Dimethoxy-1,2-diphenylethyl-1-one antioxidants β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester

[0055] Hybrid process

[0056] All component ratios in the mixing process are by weight. At room temperature, the plasticizer and solid rubber are mixed at a plasticizer:solid rubber ratio of 1:5. The mixture is poured into a mixer preheated to 140°C and rotating at 50 rpm. Then, the acrylate compound is added to the mixer at an acrylate:solid rubber ratio of 1:10. After adding all the preceding components, the reactive monomer is added and mixed for 4-5 minutes. Then, the photoinitiator is added at 2% of the sum of the weights of the solid rubber and acrylate compound, and the mixture is quickly mixed. After mixing, the mixture is removed and cooled to room temperature before use.

[0057] Board making process

[0058] The aforementioned mixture was sandwiched between a polyester film support coated with a thermoplastic elastomer adhesive and having a thickness of 125 micrometers, and a polyester cover sheet having a polyamide layer with a thickness of 4 micrometers and a thickness of 100 micrometers, using 2.5 mm spacers, and pressurized at 130°C and 200 kg / cm². 2 After applying pressure for 4 minutes, a photosensitive structure for flexible printing plates is obtained.

[0059] Remove the cover sheet of the aforementioned photosensitive structure, allowing the negative to adhere tightly to the polyamide protective layer on the photopolymerizable composition layer for flexible printed circuit boards. Using an AFT-1500 exposure machine (ASAHI KASEI E-materials Corp.) and a 370nm center wavelength ultraviolet fluorescent lamp, first expose the negative to 240mJ / cm² light from the support side. 2 Full-area exposure. Then, through negative film, apply 8000 mJ / cm². 2 The image was exposed.

[0060] The plate is glued to the rotating barrel of an AFP-1500 developer (Asahi-Kasei Chemocals Corporation), developed in 3-methoxybutyl acetate developer at 25°C for 5 minutes, and then dried at 60°C for 2 hours.

[0061] The UV dose for the following curing processes was measured using a small UV radiation meter (such as UV Process Supply Inc.).

[0062] A germicidal lamp with a center wavelength of 254nm was used to disinfect the entire surface of the plate at 1000mJ / cm². 2 Post-exposure, followed by UV fluorescent lamp at 1000 mJ / cm 2 The subsequent exposure yields the desired flexible printed circuit board.

[0063] Related tests

[0064] The content of vinyl aromatics in vinyl aromatic block and ternary random copolymer blocks can be determined by (1H-NMR) nuclear magnetic resonance.

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

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

[0067] UV transmittance: Transmittance is the ratio of UV intensity when a plate on a miniature UV radiometer passes under a UV lamp, with and without the plate. The plate thickness is 2mm.

[0068] Gel content: After weighing the test plate, immerse it in a large amount of toluene overnight, filter out the undissolved portion, and dry it in a vacuum at 70°C until the weight no longer decreases. Gel content (%) = W 干燥 / W 起始 *100, where W 干燥 W represents the weight of the undissolved portion after soaking in toluene overnight, after drying. 起始 This represents the weight of the plate being measured before immersion in toluene.

[0069] Damage resistance: Flexible printing plates are prepared using negatives with 8-12 dot characters. The degree of damage to the characters is observed after about 300 rubs using an NP-type rubbing force tester (the contact body is cloth, the size is 8cm x 6cm, and the load is 1kg).

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

[0071] Table 4

[0072] SIS / SBS ​​weight ratio (wt%) Reflectance 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 whitewash 0.0

[0073] As shown in Table 4, the reflectance of pure SIS and SBS at 400nm is 2.9% and 1.6%, respectively. Such reflectance indicates that the transparency of the printing plates made from the pure components of both is quite excellent.

[0074] However, the drawback is that, with the aforementioned mixtures, except for the SIS / SBS ​​ratio of 10 / 90 (reflectance of 2.7%), the other ratios exhibit low transmittance and high reflectance (above 3%), especially in the 20 / 80–80 / 20 range, and even more pronounced between 30 / 70–70 / 30, where reflectance reaches its maximum. Reflectance in the 20 / 80–80 / 20 range corresponds to a white, milky, cloudy appearance within the sample. Therefore, users can only use nearly pure SIS or SBS polymers to prepare adhesives or flexible printing plates with low scattering and high transparency, and cannot formulate intermediate formulations with acceptable high transmittance / low reflectance using such SIS and SBS. However, intermediate formulations offer formulators much greater flexibility in adjusting the properties of SIS and SBS, making them necessary and essential.

[0075] The data in Table 5 show that by combining the properties of SIS and SBS polymers, technicians can improve some of the shortcomings of SIS or SBS polymers alone, such as improving the degradation of SIS (increased MFR) and the gelation caused by SBS crosslinking during processing (typically at processing temperatures of 140°C to 180°C) while maintaining excellent transparency.

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

[0077] Table 5

[0078]

[0079] The rubber sheet composition of the printing plates in the embodiments and comparative examples obtained with the different thermoplastic elastomers described above is shown in Table 6, and the transparency of the resulting printing plates is also provided.

[0080] Table 6 shows the transparency of the printing plates obtained in Examples 1-10 and Comparative Examples 1-6.

[0081]

[0082]

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

[0084] Example 1: Linear S(S / I / B)S was prepared according to the above block polymer preparation method, and then a flexible printed circuit board was obtained by the above mixing process and board making process, and then various tests were performed.

[0085] The block polymer preparation methods of the remaining embodiments and comparative examples are basically the same as those of the block polymers described above. 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 segment.

[0086] The mixing and board-making processes used in the remaining embodiments and comparative examples are exactly the same. The difference lies in the type and proportion of solid rubber used. The specific types and proportions are shown in Table 6.

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

[0088] By comparing the data of the three samples marked with **, it can be directly observed that S(S / I / B)S and (S(S / I / B))nX have a very significant compatibilizing effect on both SIS and SBS. While the UV transmittance is barely acceptable, it is close to the threshold value. This data indicates that at least 30% of S(S / I / B)S or (S(S / I / B))nX needs to be used in the mixture for printing plates with lower resolution requirements. If higher resolution is required, the amount of block polymer used in this invention must be increased.

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

[0090] Table 7 shows the results of the damage resistance test. "O" indicates that the text is undamaged, and "X" indicates that the text is damaged.

[0091] Table 7 shows the results of the defect resistance test of the printing plates obtained in Examples 1-10 and Comparative Examples 1-6.

[0092] Rubber sheet composition Results of 5 defect tests 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 O OOXX Comparative Example 6 (SI)nX O OOO X Comparative Example 7 (SB)nX O OXXX Comparative Example 8 (SIB)nX O OOXX Example 1 S(S / I / B)S O OOOO Example 2 S(S / I / B)S O OOOO Example 3 (S(S / I / B))nX O OOOO Example 4 (S(S / I / B))nX O OOOO Example 5 S(S / I / B)S+SIS;50 / 50 O OOOO 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 O OOOO Example 10 (S(S / I / B))nX + liquid PB; 85 / 15 O OOOO

[0093] As can be seen from the test results in Table 7, the photopolymerizable composition containing the controlled-distribution block polymer of the present invention shows a significant advantage in terms of the defect resistance of the manufactured printing plate.

Claims

1. A composition of a photopolymerizable controlled-distribution block polymer, characterized in that: The composition includes a block polymer, an acrylate compound, and a polymerization initiator; the mass ratio of the block polymer to the acrylate compound is 0.3~98:1; the amount of the polymerization initiator added is 0.5~10 wt% of the composition mass. 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 blocks with a number average molecular weight of 7000-40000, C is a vinyl aromatic-isoprene-butadiene random copolymer block, n is an integer greater than or equal to 2, and X is a coupling agent residue; the polyvinyl aromatic content in the thermoplastic elastomer copolymer is 18-30 wt%. The number of monomer units contained in C is ≤20; the content of vinyl aromatic monomers in C is 3~10wt%.

2. The composition of a photopolymerizable controlled-distribution block polymer according to claim 1, characterized in that: The composition further includes functional additives, the amount of which is not more than 40% of the total mass of the composition; the functional additives are at least one of plasticizers, antioxidants, polymerization inhibitors, pigments, and rubbers 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 15~35wt%; the polyvinyl aromatic hydrocarbon is obtained by polymerization of at least one of styrene, C1~C4 alkylstyrene and C1~C4 dialkylstyrene.

4. The composition of a photopolymerizable controlled-distribution block polymer according to claim 1, characterized in that: The number average molecular weights of S1, S2 and S are 10,000 to 25,000.

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 percentage of S1-C-S2 and / or (SC)nX in the block polymer is ≥30%.

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

1.

7. The composition of a photopolymerizable controlled-distribution block polymer according to claim 6, characterized in that: The acrylate compound is at least one selected from butyl acrylate, isodecanyl acrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, and dipentaerythritol monohydroxypentaacrylate.

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

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

10. A method for preparing a composition of a photopolymerizable controlled-distribution block polymer according to any one of claims 1 to 9, characterized in that: Initiate the polymerization of vinyl aromatics by uniformly mixing an inert solvent, vinyl aromatic monomers, regulators, and initiators. After polymerization is complete, add isoprene and butadiene and mix thoroughly. Use a starvation polymerization method. After starvation polymerization is complete, add vinyl aromatic monomers again for polymerization or add a coupling agent for coupling reaction. Add a terminator at the end of the reaction to obtain the block polymer. Alternatively, mix an inert solvent, vinyl aromatic monomers, a mixture of isoprene and butadiene, regulators, and initiators for polymerization. Add vinyl aromatic monomers again at the end of the reaction to obtain the block polymer. Mix the block polymer and functional additives thoroughly and add them to a preheated mixer. Add acrylate compounds and polymerization initiators in sequence, mix thoroughly, and cool to room temperature to obtain the final product.

11. The method for preparing a composition of a photopolymerizable controlled-distribution block polymer according to claim 10, characterized in that: The solvent is at least one selected from cyclopentane, cyclohexane, and n-hexane; the terminator is one selected from methanol, ethanol, water, phenols, and organic acids; the regulator is at least one selected from 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; and the coupling agent is a silane coupling agent, an alkoxysilane, a tin coupling agent, a divinyl aromatic compound, a haloalkane, and an epoxy compound.

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

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

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