Multi-unsaturation flexible prepolymer modified water-based self-extinction acrylic resin and preparation method thereof
By introducing polyunsaturation flexible prepolymers of polyamine heterocyclic compounds into the acrylate copolymer, a polyunsaturation flexible chain grafting flexible chains is formed, and the complexity and cost of traditional matting coating equipment is solved, and a coating with excellent self-matting effect and performance is achieved.
Patent Information
- Application Number
- CN202510392178.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-07-04
AI Technical Summary
Traditional matting coatings use water-based polyurethane resins to require reverse phase conversion, the equipment process is complex and the amount of matting agent powder is large, which affects the coating performance and increases costs.
The flexible chain is grafted with polyamine heterocyclic compounds as the center point to form a polyunsaturated flexible prepolymer with acrylic double bond at the end base, and the island structure is formed into the acrylic ester copolymer, and the phase separation characteristics of the flexible prepolymer and the hard segment are used to achieve self-extinction.
Through molecular structure design, microscopic roughness is formed, the coating self-massing effect is achieved, the gloss and coating performance is maintained, avoiding the increase in equipment complexity and cost of traditional methods.
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Figure CN120248235A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of industrial coating resin synthesis, and in particular to a polyunsaturated flexible prepolymer modified water-based self-matting acrylic resin and a preparation method thereof. Background Art
[0002] With the emergence of light pollution and the evolution of aesthetic needs, consumers are increasingly favoring the restrained and low-key matte texture. Matt coatings are widely used in wall coatings, wood coatings, paper coatings, leather decoration and vehicle interiors due to their excellent glare suppression and surface defect masking capabilities.
[0003] The resin used in traditional matte coatings is water-based polyurethane, which requires phase inversion and has high requirements on equipment and process. At the same time, a large amount of matte agent powder needs to be added, which has a negative impact on the physical and mechanical properties of the coating and greatly increases the cost of the product. Summary of the invention
[0004] To this end, the technical problem to be solved by the present invention is to provide a polyunsaturated flexible prepolymer modified water-based self-matting acrylic resin and a preparation method thereof. Through molecular structure design, a polyamine heterocyclic compound is used as the center point, and multiple flexible chains are grafted thereon to form a polyunsaturated flexible prepolymer with an acrylic double bond at the end group. This dendritic compound with a double bond at the end group is introduced into an acrylic ester copolymer to form an island structure.
[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:
[0006] A polyunsaturated flexible prepolymer modified water-based self-matting acrylic resin, comprising the following components: 100 parts by weight of methyl methacrylate, 50-100 parts by weight of styrene, 50-100 parts by weight of isooctyl acrylate, 10-20 parts by weight of hydroxyethyl acrylate, 5-10 parts by weight of acrylic acid, 10-40 parts by weight of polyunsaturated flexible prepolymer, 0.5 parts by weight of ammonium persulfate, 1-5 parts by weight of emulsifier, 1-2 parts by weight of sodium bicarbonate and 200 parts by weight of deionized water; wherein the polyunsaturated flexible prepolymer is prepared by the following steps:
[0007] a) Preparation of materials: raw materials are prepared according to the following components: the polyunsaturated flexible prepolymer is obtained by reacting 100 parts by weight of a flexible monomer, 20 to 60 parts by weight of a polyamine heterocyclic compound, 10 to 30 parts by weight of a modified monomer, 1 to 3 parts by weight of a catalyst I and 1 to 3 parts by weight of a catalyst II, wherein the flexible monomer is a flexible monomer having at least two epoxy terminal groups, and the polyamine heterocyclic compound is a polyamine heterocyclic compound having at least two primary amines or secondary amines or one primary amine and one secondary amine;
[0008] b) Add the flexible monomer and the azine compound in step a) into a reaction kettle, keep it at a low temperature of -10 to 0 °C under stirring conditions, and then add catalyst I and react for 2 to 4 hours;
[0009] c) After the reaction in step b) is completed, add the modified monomer into the reaction kettle, heat it to 50 to 60 °C under stirring conditions, and then add catalyst II and react for 2 to 4 hours;
[0010] d) After the reaction in step c) is completed, cool it to room temperature and discharge, then the poly-unsaturation flexible prepolymer is obtained.
[0011] For the above-mentioned poly-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin, the polyamine heterocyclic compound is 1,4-bis(3-aminopropyl)piperazine or 3,6-dihydrazino-1,2,4,5-tetrazine.
[0012] For the above-mentioned poly-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin, the flexible monomer is one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and neopentyl glycol diglycidyl ether.
[0013] For the above-mentioned poly-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin, the modified monomer is one of acrylic acid, methacrylic acid and itaconic acid.
[0014] For the above-mentioned poly-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin, the catalyst I is one or more of triethylamine, triethylenediamine and 2-methylimidazole.
[0015] For the above-mentioned poly-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin, the catalyst II is one or more of triethylamine, 4-dimethylaminopyridine and bicyclic amidine.
[0016] For the above-mentioned poly-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin, the emulsifier is one or more of sodium dodecylbenzenesulfonate, polyoxyethylene ether sulfate and alkyl polyoxyethylene ether surfactant.
[0017] The preparation method of the above-mentioned poly-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin includes the following steps:
[0018] 1) Prepare materials: according to the following ratio: 100 parts by weight of methyl methacrylate, 50 to 100 parts by weight of styrene, 50 - 100 parts by weight of isooctyl acrylate, 10 to 20 parts by weight of hydroxyethyl acrylate, 5 to 10 parts by weight of acrylic acid, 10 - 40 parts by weight of poly-unsaturation flexible prepolymer, 0.5 part by weight of ammonium persulfate, 1 to 5 parts by weight of emulsifier, 1 to 2 parts by weight of sodium bicarbonate and 200 parts by weight of deionized water;
[0019] 2) Mix methyl methacrylate, styrene, isooctyl acrylate, 2-hydroxyethyl acrylate and acrylic acid to form an oil phase;
[0020] 3) Add emulsifier and sodium bicarbonate to water to form an aqueous phase, and add the oil phase to the aqueous phase and stir to obtain a pre-emulsion;
[0021] 4) Add 10% of the pre-emulsion to the reaction kettle, stir and heat up to 80 °C, add 10% of ammonium persulfate, and react for 20 min;
[0022] 5) Heat up to 85 °C, add the polyunsaturated and flexible prepolymer to the reaction kettle, and then dropwise add the remaining pre-emulsion and the remaining ammonium persulfate;
[0023] 6) After the feeding is completed, keep the temperature for reaction for 1.5 hours, and then cool and discharge.
[0024] In the above preparation method, in step 1), after the preparation is completed, the polyunsaturated flexible prepolymer is divided into three parts;
[0025] In step 5), add the polyunsaturated flexible prepolymer to the reaction kettle and dropwise add the remaining pre-emulsion and the remaining ammonium persulfate according to the following operation:
[0026] The first stage: Dropwise add 30% of the pre-emulsion and 30% of ammonium persulfate. After 30 minutes, add the first part of the polyunsaturated flexible prepolymer and dropwise add for 20 minutes;
[0027] The second stage: Continue to dropwise add 30% of the pre-emulsion and 30% of ammonium persulfate. After 30 minutes, add the second part of the polyunsaturated flexible prepolymer and dropwise add for 20 minutes;
[0028] The third stage: Dropwise add the remaining pre-emulsion and the remaining ammonium persulfate. After 30 minutes, add the third part of the polyunsaturated flexible prepolymer and dropwise add for 20 minutes;
[0029] In the above preparation method, the weight ratio of the first part of the polyunsaturated flexible prepolymer, the second part of the polyunsaturated flexible prepolymer and the third part of the polyunsaturated flexible prepolymer is (0-1):(0-1):(0-1), and at least two of the first part of the polyunsaturated flexible prepolymer, the second part of the polyunsaturated flexible prepolymer and the third part of the polyunsaturated flexible prepolymer have a non-zero weight.
[0030] The technical solution of the present invention has achieved the following beneficial technical effects:
[0031] Through molecular structure design, the present invention uses polyamine heterocyclic compounds as the center point, grafts multiple flexible chains thereon to form a multi-unsaturated flexible prepolymer with acrylic double bonds at the end groups. This dendritic compound with double bonds at the end groups is introduced into the acrylate copolymer to form a sea-island structure. Among them, the multi-unsaturated flexible prepolymer serves as the soft segment, and the acrylate copolymer with a high Tg serves as the hard segment. Utilizing the phase separation characteristics of the two, the film forms microscopic roughness due to the curing difference between the two phases during the drying process, thereby achieving the self-extinction of the coating. Description of the Drawings
[0032] Figure 1 It is the chemical structural formula of the multi-unsaturated flexible prepolymer prepared in Example 1;
[0033] Figure 2 It is the chemical structural formula of the multi-unsaturated flexible prepolymer prepared in Example 12. Detailed Embodiments
[0034] Example 1
[0035] In this example, the multi-unsaturated flexible prepolymer-modified waterborne self-extinguishing acrylic resin is prepared from 100 parts by weight of methyl methacrylate, 50 parts by weight of styrene, 50 parts by weight of isooctyl acrylate, 15 parts by weight of hydroxyethyl acrylate, 7 parts by weight of acrylic acid, 10 parts by weight of the multi-unsaturated flexible prepolymer, 0.5 parts by weight of ammonium persulfate, 2.5 parts by weight of sodium dodecylbenzenesulfonate and alkyl polyoxyethylene ether, 1.5 parts by weight of sodium bicarbonate and 200 parts by weight of deionized water. The specific process is as follows: Mix methyl methacrylate, styrene, isooctyl acrylate, hydroxyethyl acrylate and acrylic acid to form an oil phase; add emulsifier and sodium bicarbonate to water to form an aqueous phase, and add the oil phase to the aqueous phase and stir to obtain a pre-emulsion; add 10% of the pre-emulsion to the reaction kettle, stir and heat up to 80 °C, add 10% of ammonium persulfate, and react for 20 min; heat up to 85 °C and start dropping the remaining pre-emulsion and the remaining ammonium persulfate; the dropping is carried out in three stages. The first stage: drop 30% of the pre-emulsion and 30% of ammonium persulfate, add 1 / 3 of the prepolymer after 30 minutes, and drop for 20 minutes; the second stage: continue to drop 30% of the pre-emulsion and 30% of ammonium persulfate, add 1 / 3 of the prepolymer after 30 minutes, and drop for 20 minutes; the third stage: drop the remaining pre-emulsion and the remaining ammonium persulfate, add the last 1 / 3 of the prepolymer after 30 minutes, and drop for 20 minutes; after the feeding is completed, keep the temperature for reaction for 1.5 hours, cool and discharge.
[0036] Among them, the multi-unsaturation flexible prepolymer is obtained by reacting 100 parts by weight of polyethylene glycol diglycidyl ether, 20 parts by weight of 1,4-bis(3-aminopropyl)piperazine, 10 parts by weight of acrylic acid, 2 parts by weight of triethylenediamine and 2 parts by weight of triethylamine. The structural formula of the multi-unsaturation flexible prepolymer in this example is as Figure 1 shown.
[0037] Example 2
[0038] The difference between the waterborne self-extinguishing acrylic resin modified with the multi-unsaturation flexible prepolymer in this example and that in Example 1 is that: in this example, the addition amount of styrene is changed to 75 parts by weight.
[0039] Example 3
[0040] The difference between the waterborne self-extinguishing acrylic resin modified with the multi-unsaturation flexible prepolymer in this example and that in Example 1 is that: in this example, the addition amount of styrene is changed to 100 parts by weight.
[0041] Example 4
[0042] The difference between the waterborne self-extinguishing acrylic resin modified with the multi-unsaturation flexible prepolymer in this example and that in Example 1 is that: in this example, the addition amount of isooctyl acrylate is changed to 75 parts by weight.
[0043] Example 5
[0044] The difference between the waterborne self-extinguishing acrylic resin modified with the multi-unsaturation flexible prepolymer in this example and that in Example 1 is that: in this example, the addition amount of isooctyl acrylate is changed to 100 parts by weight.
[0045] Example 6
[0046] The difference between the waterborne self-extinguishing acrylic resin modified with the multi-unsaturation flexible prepolymer in this example and that in Example 1 is that: in this example, the addition amount of the multi-unsaturation flexible prepolymer is changed to 25 parts by weight.
[0047] Example 7
[0048] The difference between the waterborne self-extinguishing acrylic resin modified with the multi-unsaturation flexible prepolymer in this example and that in Example 1 is that: in this example, the addition amount of the multi-unsaturation flexible prepolymer is changed to 40 parts by weight.
[0049] Example 8
[0050] The difference between the waterborne self-extinguishing acrylic resin modified with the multi-unsaturation flexible prepolymer in this example and that in Example 1 is that: in this example, the addition amount of the piperazine compound in the preparation process of the multi-unsaturation flexible prepolymer is changed to 40 parts by weight.
[0051] Example 9
[0052] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that: in this example, the addition amount of the azine compound in the preparation process of the multi-unsaturation flexible prepolymer is changed to 60 parts by weight.
[0053] Example 10
[0054] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that: in this example, the addition amount of the modified monomer in the preparation process of the multi-unsaturation flexible prepolymer is changed to 20 parts by weight
[0055] Example 11
[0056] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that: in this example, the addition amount of the modified monomer in the preparation process of the multi-unsaturation flexible prepolymer is changed to 30 parts by weight.
[0057] Example 12
[0058] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that: in this example, the azine compound in the preparation process of the multi-unsaturation flexible prepolymer is changed to 3,6-dihydrazino-1,2,4,5-tetrazine, and the structural formula of the multi-unsaturation flexible prepolymer is as Figure 2 shown.
[0059] Example 13
[0060] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that: in this example, the flexible monomer in the preparation process of the multi-unsaturation flexible prepolymer is changed to polypropylene glycol diglycidyl ether.
[0061] Example 14
[0062] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that: in this example, the modified monomer in the preparation process of the multi-unsaturation flexible prepolymer is changed to itaconic acid.
[0063] Example 15
[0064] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that: in this example, the catalyst 1 in the preparation process of the multi-unsaturation flexible prepolymer is changed to 2-methylimidazole.
[0065] Example 16
[0066] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that in this example, catalyst 2 in the preparation process of the multi-unsaturation flexible prepolymer is changed to 4-dimethylaminopyridine.
[0067] Example 17
[0068] The difference between the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin in this example and that in Example 1 is that in this example, the emulsifier is changed to polyoxyethylene ether sulfate and alkyl polyoxyethylene ether.
[0069] Comparative Example
[0070] The difference between the comparative example and Example 1 is that the multi-unsaturation flexible prepolymer is replaced with a prepolymer without multi-unsaturation flexible prepolymer.
[0071] Test method:
[0072] (1) The emulsion particle size is detected by a Malvern laser particle size analyzer;
[0073] (2) Use a 20μm wire bar coater to coat about 1g of the waterborne matte acrylic emulsion on a specific cardboard (6cm×6cm), dry to the touch for 10min, then put it into a forced air drying oven and dry at 120°C for 10min to prepare a film with a thickness of about 10μm for measuring other physical properties.
[0074] Table 1 Comparison of emulsion properties
[0075] Sample Name Particle Size / nm Film Gloss (60-degree Angle) Adhesion Hardness Example 1 237 26 Grade 0 2B Example 2 252 25 Grade 0 2B Example 3 278 24 Grade 1 1B Example 4 201 28 Grade 0 2B Example 5 183 30 Grade 0 2B Example 6 214 21 Grade 1 2B Example 7 198 16 Grade 1 2B Example 8 266 21 Grade 0 2B Example 9 294 16 Grade 1 1B Example 10 219 22 Grade 0 2B Example 11 202 18 Grade 0 1B Example 12 275 21 Grade 0 1B Example 13 257 23 Grade 1 2B Example 14 244 23 Grade 1 1B Example 15 231 25 Grade 0 2B Example 16 241 26 Grade 0 2B Example 17 225 25 Grade 0 2B Comparative Example 262 60 Grade 1 4B
[0076] From the data recorded in Table 1, it can be seen that when the adhesion changes little or does not change, the gloss of the paint film decreases significantly, which indicates that the multi-unsaturation flexible prepolymer in the present invention can significantly reduce the gloss of the acrylic resin. From the gloss of the paint films prepared from the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resins in Example 1, Example 6 and Example 7, it can be seen that as the amount of the multi-unsaturation flexible prepolymer used increases, the gloss of the paint film decreases significantly. And from the gloss of the paint films prepared from the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resins in Example 1, Example 8 and Example 9, it can be seen that when the same weight of the multi-unsaturation flexible prepolymer is used, an increase in the amount of the quinazoline compound in the multi-unsaturation flexible prepolymer will also significantly reduce the gloss of the paint film.
[0077] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the claims of this patent application.
Claims
1. A multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin, characterized in that, It consists of the following components: 100 parts by weight of methyl methacrylate, 50 to 100 parts by weight of styrene, 50 - 100 parts by weight of isooctyl acrylate, 10 to 20 parts by weight of 2-hydroxyethyl acrylate, 5 to 10 parts by weight of acrylic acid, 10 - 40 parts by weight of a poly-unsaturation flexible prepolymer, 0.5 part by weight of ammonium persulfate, 1 - 5 parts by weight of an emulsifier, 1 - 2 parts by weight of sodium bicarbonate, and 200 parts by weight of deionized water; wherein, the poly-unsaturation flexible prepolymer is prepared through the following steps: a) Preparation of materials: Prepare raw materials according to the following components: The poly-unsaturation flexible prepolymer is obtained by reacting 100 parts by weight of a flexible monomer, 20 - 60 parts by weight of a polyamine heterocyclic compound, 10 - 30 parts by weight of a modified monomer, 1 - 3 parts by weight of catalyst I, and 1 - 3 parts by weight of catalyst II, wherein the flexible monomer is a flexible monomer having at least two epoxy end groups, and the polyamine heterocyclic compound is a polyamine heterocyclic compound having at least two primary amines or hydrazines or one primary amine and one hydrazine; b) Add the flexible monomer and the azine compound in step a) into a reaction kettle, maintain a low temperature of -10 to 0 °C under stirring conditions, and then add catalyst I and react for 2 - 4 hours; c) After the reaction in step b) ends, add the modified monomer into the reaction kettle, raise the temperature to 50 - 60 °C under stirring conditions, and then add catalyst II and react for 2 - 4 hours; d) After the reaction in step c) ends, cool to room temperature and discharge to obtain the poly-unsaturation flexible prepolymer.
2. The multi-unsaturation flexible prepolymer-modified waterborne self-extinguishing acrylic resin according to claim 1, characterized in that The polyamine heterocyclic compound is 1,4-bis(3-aminopropyl)piperazine or 3,6-dihydrazino-1,2,4,5-tetrazine.
3. The multi-unsaturation flexible prepolymer-modified waterborne self-extinguishing acrylic resin according to claim 1, wherein The flexible monomer is one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether.
4. The multi-unsaturation flexible prepolymer-modified waterborne self-extinguishing acrylic resin according to claim 1, wherein, The modified monomer is one of acrylic acid, methacrylic acid, and itaconic acid.
5. The multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin according to claim 1, characterized in that, The catalyst I is one or more of triethylamine, triethylenediamine, and 2-methylimidazole.
6. The multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin according to claim 1, characterized in that The catalyst II is one or more of triethylamine, 4-dimethylaminopyridine, and bicyclic amidine.
7. The multi-unsaturation flexible prepolymer-modified waterborne self-extinguishing acrylic resin according to claim 1, characterized in that, The emulsifier is one or more of sodium dodecylbenzenesulfonate, polyoxyethylene ether sulfate, and alkyl polyoxyethylene ether surfactant.
8. The preparation method of the multi-unsaturation flexible prepolymer modified waterborne self-extinguishing acrylic resin as described in claim 1, characterized in that, It includes the following steps: 1) Preparation of materials: According to the following ratio: 100 parts by weight of methyl methacrylate, 50 - 100 parts by weight of styrene, 50 - 100 parts by weight of isooctyl acrylate, 10 - 20 parts by weight of 2-hydroxyethyl acrylate, 5 - 10 parts by weight of acrylic acid, 10 - 40 parts by weight of a poly-unsaturation flexible prepolymer, 0.5 part by weight of ammonium persulfate, 1 - 5 parts by weight of an emulsifier, 1 - 2 parts by weight of sodium bicarbonate, and 200 parts by weight of deionized water; 2) Mix methyl methacrylate, styrene, isooctyl acrylate, 2-hydroxyethyl acrylate, and acrylic acid to form an oil phase; 3) Add the emulsifier and sodium bicarbonate into water to form an aqueous phase, and add the oil phase into the aqueous phase and stir to obtain a pre-emulsion; 4) Add 10% of the pre-emulsion into a reaction kettle, stir and heat up to 80 °C, add 10% of ammonium persulfate, and react for 20 min; 5) Heat up to 85°C, add the polyunsaturated and flexible prepolymer into the reaction kettle, and then dropwise add the remaining pre-emulsion and the remaining ammonium persulfate; 6) After the feeding is completed, keep the temperature for reaction for 1.5 hours, and then cool and discharge.
9. According to the preparation method described in claim 8, it is characterized in that, In step 1), after the preparation is completed, divide the polyunsaturated flexible prepolymer into three portions; In step 5), add the polyunsaturated flexible prepolymer into the reaction kettle and dropwise add the remaining pre-emulsion and the remaining ammonium persulfate according to the following operation: The first stage: Dropwise add 30% of the pre-emulsion and 30% of the ammonium persulfate. After 30 minutes, add the first portion of the polyunsaturated flexible prepolymer and dropwise add for 20 minutes; The second stage: Continue to dropwise add 30% of the pre-emulsion and 30% of the ammonium persulfate. After 30 minutes, add the second portion of the polyunsaturated flexible prepolymer and dropwise add for 20 minutes; The third stage: Dropwise add the remaining pre-emulsion and the remaining ammonium persulfate. After 30 minutes, add the third portion of the polyunsaturated flexible prepolymer and dropwise add for 20 minutes.
10. According to the preparation method described in claim 9, characterized in that, The weight ratio of the first portion of the polyunsaturated flexible prepolymer, the second portion of the polyunsaturated flexible prepolymer, and the third portion of the polyunsaturated flexible prepolymer is (0-1):(0-1):(0-1), and at least two of the first portion of the polyunsaturated flexible prepolymer, the second portion of the polyunsaturated flexible prepolymer, and the third portion of the polyunsaturated flexible prepolymer have non-zero weights.