A modified polyolefin defoamer for epoxy resin and its preparation method and application

Abstract

The application belongs to the technical field of polymer material processing aids, and relates to a modified polyolefin defoaming agent for epoxy resin and a preparation method and application thereof. The defoaming agent has a general formula P-O-L-X (I) structure, P is a polyolefin hydrophobic chain segment with a specific number average molecular weight, O is a connecting group, L is a hydrophilic-polar chain segment, and X is an epoxy affinity functional group. The preparation method comprises an end group modification method and a graft modification method. The defoaming agent is applied in an epoxy resin composition, and the composition contains an epoxy resin, a curing agent and the defoaming agent. Through unique molecular structure design, the defoaming agent realizes high balance between defoaming activity and system compatibility, has excellent compatibility and transparency, high-efficiency and long-lasting defoaming property, does not affect the performance of a final material, has wide applicability, has a clear structure and controllable performance, and solves the problem that traditional defoaming agents are difficult to be compatible and have defoaming efficiency in epoxy resin.

Description

Technical Field

[0001] This invention relates to the field of polymer processing aids, specifically to a defoamer for epoxy resin systems, particularly a defoamer based on a modified polyolefin structure that exhibits excellent compatibility with epoxy resins, maintains high transparency of the system, and its preparation method. Background Technology

[0002] Epoxy resins are widely used in electronic packaging, composite materials, coatings, and adhesives due to their excellent adhesion, mechanical strength, electrical insulation, and chemical stability. However, during their preparation, mixing, potting, and spraying processes, air bubbles are easily incorporated. If these bubbles are not eliminated promptly, they will form defects after curing, severely affecting the mechanical properties, electrical properties, appearance, and reliability of the product.

[0003] Currently, commonly used defoamers in epoxy resin systems are mainly silicone-based (polydimethylsiloxane and its modified forms) and non-silicone polymers (such as polyethers and polyacrylates). However, these traditional defoamers have significant shortcomings when applied to epoxy systems with strict transparency requirements (such as optical adhesives, transparent potting compounds, and crystal epoxy resins). 1. Poor compatibility leads to deterioration of transparency: Organosilicon defoamers have limited compatibility with polar epoxy resins, which easily leads to micro-phase separation, resulting in turbidity, increased haze, and even oil spots and pinholes, which seriously affect optical transparency.

[0004] 2. Affects surface properties: Organosilicon is easy to migrate to the surface, which may result in the coating surface energy being too low, affecting subsequent spraying, printing or bonding.

[0005] 3. It is difficult to balance the defoaming efficiency and compatibility of non-silicone defoamers: Some polyacrylate defoamers have improved compatibility, but their defoaming efficiency (especially foam suppression performance) is often inferior to that of silicone defoamers, and may introduce color or affect curing.

[0006] Therefore, developing a specialized defoamer that can efficiently defoam and suppress foam, is perfectly compatible with epoxy resin, and does not impair its optical transparency has become a pressing technical challenge in the field of high-end epoxy resin applications. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an epoxy resin defoamer based on modified polyolefins. This defoamer, through molecular structure design, introduces polar functional groups with strong interactions with epoxy resins onto the polyolefin backbone, achieving a high balance between defoaming activity and system compatibility.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned defoamer.

[0009] Another object of the present invention is to provide the use of the above-mentioned defoamer in transparent or non-transparent epoxy resin compositions.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a modified polyolefin defoamer for epoxy resins, characterized in that the defoamer is a polymer having the structure shown in the following general formula (I): POLX (I) In the formula: - P is a hydrophobic segment of a polyolefin, selected from polyisobutylene (PIB), hydrogenated polybutadiene (HPBD), ethylene-propylene copolymer, or propylene-α-olefin copolymer with a number-average molecular weight (Mn) of 800-5000 g / mol. This segment provides low surface tension and the necessary hydrophobicity, and is the core of the defoaming function, promoting the migration of the defoamer to the bubble interface.

[0011] -O is a linking group, which can be a direct chemical bond or a short chain containing ester, amide, or carbamate groups. It is used to link hydrophobic and polar segments.

[0012] - L is a hydrophilic-polar segment selected from polyethylene oxide (PEO) segments, polypropylene oxide (PPO) segments, or copolymer segments thereof, with a number-average molecular weight of 200-1000 g / mol; or a C2-C12 alkyl chain containing hydroxyl and carboxyl groups. This segment provides moderate hydrophilicity and initial compatibility with epoxy resins.

[0013] - X is an epoxy affinity functional group, selected from at least one of epoxy, carboxyl, acid anhydride, primary or secondary amine, hydroxyl, and silanoxy groups. This functional group can physically interact (such as with hydrogen bonds) or slightly chemically react with the epoxy or hydroxyl groups of the epoxy resin, ensuring that the defoamer molecules can be stably dispersed or "anchored" in the epoxy resin matrix, preventing phase separation.

[0014] Preferably, the hydrophobic segment P of the polyolefin is polyisobutylene or hydrogenated polybutadiene with Mn=1000-3000 g / mol.

[0015] Preferably, the epoxy affinity functional group X is an epoxy group, an anhydride group, or a silaneoxy group. These groups have excellent compatibility with epoxy resins and their reactivity is controllable.

[0016] Preferably, the defoamer has a number-average molecular weight (Mn) of 1500-8000 g / mol and a molecular weight distribution (K) of 1.05-1.50. A narrow molecular weight distribution contributes to the uniformity and predictability of performance.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned modified polyolefin defoamer, comprising the following steps: Route A (End-group modification method): 1. Select polyolefins with active groups (such as hydroxyl-terminated polyisobutylene and carboxyl-terminated hydrogenated polybutadiene) at one or both ends as raw materials.

[0018] 2. In the presence of a catalyst, the active end group of the polyolefin is reacted with a compound containing an epoxy-affinity functional group X (such as glycidyl ether, acid anhydride, silane coupling agent) and optionally a bifunctional linker to introduce linking group O and functional group X.

[0019] 3. Alternatively, the polyolefin can be reacted with a low molecular weight polyether (such as monomethyl ether polyethylene glycol) to introduce segment L, and then the end of the polyether can be modified to introduce functional group X.

[0020] 4. The target defoamer is obtained after purification.

[0021] Route B (grafting modification method): 1. Select polyolefins containing unsaturated double bonds (such as polybutadiene) or polyolefins that can generate active sites on the main chain.

[0022] 2. By using free radical graft copolymerization or anionic grafting techniques, monomers containing functional group X (such as glycidyl methacrylate and maleic anhydride) are reacted with polyolefins to graft polar side chains onto the main chain.

[0023] 3. Perform possible post-treatments such as hydrogenation and end-capping on the grafted product to obtain the target defoamer.

[0024] Thirdly, the present invention provides the use of the above-described modified polyolefin defoamer in epoxy resin compositions. **The epoxy resin composition comprises an epoxy resin, a curing agent, and optionally accelerators, fillers, pigments, and other additives.

[0025] Fourthly, the present invention provides an epoxy resin composition, characterized in that it comprises: - Epoxy resin: 100 parts by weight; - Curing agent: The amount used should be matched to the equivalent amount of epoxy resin; - Modified polyolefin defoamer as described in the first aspect: 0.01-2.0 parts by weight, preferably 0.05-0.5 parts by weight.

[0026] The beneficial effects of this invention are: 1. Excellent compatibility and transparency: By introducing epoxy affinity functional groups (X), the defoamer molecules interact strongly with the epoxy resin matrix, achieving nanoscale or even molecular-level dispersion. This fundamentally avoids the problems of system turbidity and increased haze caused by phase separation, making it particularly suitable for applications requiring high transparency.

[0027] 2. Highly efficient and long-lasting defoaming performance: The hydrophobic segments (P) of polyolefins provide excellent hydrophobicity and low surface tension, enabling them to rapidly migrate to the bubble interface, disrupting the elasticity of the bubble film and promoting bubble coalescence and rupture. Simultaneously, their good bonding with the resin prevents them from failing due to excessive migration, providing a long-lasting defoaming effect.

[0028] 3. Does not affect the final material properties: Due to its good compatibility, the defoamer will not accumulate at the interface to form a weak boundary layer. Therefore, it has minimal impact on the mechanical properties (especially interlaminar shear strength and adhesion), electrical insulation and chemical resistance of the cured material.

[0029] 4. Wide applicability: By adjusting the type and length of the P-segment and the type of the X-functional group, it can be flexibly adapted to epoxy resins with different viscosities and different curing systems (amines, anhydrides, etc.).

[0030] 5. Well-defined structure and controllable performance: Based on a well-defined polymer structure design, the product quality is stable, and the defoaming effect and compatibility are predictable and controllable. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Example 1: Preparation of epoxy-terminated polyisobutylene-polyether defoamer (PIB-PEO-EP) 1. In a dry reaction flask, add 100g of hydroxyl-terminated polyisobutylene (PIB-OH) with Mn≈2000 and 150g of toluene, and heat to 80℃ under nitrogen protection.

[0033] 2. Add dicyclohexylcarbodiimide (DCC) catalyst, and slowly add 45g of monomethoxy polyethylene glycol (Mn=350) succinic acid monoester (providing L segments and some O groups), and react for 4 hours.

[0034] 3. Cool to 60°C, add 10g of excess epichlorohydrin and a small amount of tetrabutylammonium bromide, and react under alkaline conditions for 3 hours to perform epoxy end-capping (introducing the X functional group).

[0035] 4. The reaction solution was washed with water, filtered, and the solvent was removed by vacuum distillation to obtain a light yellow viscous liquid product A. GPC analysis showed Mn≈2800 and K=1.2.

[0036] Example 2: Preparation of Hydrogenated Polybutadiene Anhydride Defoamer (HPBD-MAH) 1. In a high-pressure reactor, add 100g of polybutadiene (1,2-structure content >70%) with Mn≈1500, 200g of xylene, and a small amount of free radical initiator (such as dicumyl peroxide).

[0037] 2. Heat to 140℃, slowly add 15g of maleic anhydride (MAH), react for 5 hours, and carry out graft copolymerization (introducing the X functional group).

[0038] 3. The reaction mixture was transferred to a hydrogenation reactor and reacted at 80°C and 3MPa hydrogen pressure for 6 hours under the action of a supported palladium catalyst to hydrogenate the unsaturated double bonds and obtain saturated polyolefin segments P.

[0039] 4. After filtration and concentration, an amber-colored viscous liquid product B was obtained. Acid value determination showed that the grafting rate met the requirements.

[0040] Comparative Example 1 Commercially available polydimethylsiloxane defoamers (general purpose).

[0041] Comparative Example 2 Commercially available non-silicone polyacrylate defoamers.

[0042] Application performance testing: Preparation of a transparent two-component epoxy resin system: - Component A: 100g of bisphenol A type epoxy resin (E-51), with the addition of the defoamer to be tested (the amount added is 0.3wt% based on the total amount of resin).

[0043] - Component B: 85g of methyltetrahydrophthalic anhydride (MeTHPA) curing agent and 0.5g of accelerator.

[0044] - Test sample preparation: After mixing components A and B, manually stir at high speed for 60 seconds to introduce a large number of air bubbles, then let stand to observe the defoaming situation, and pour into a flat mold for programmed temperature rise and curing.

[0045] 1. Defoaming speed and foam suppression: Record the time required for the bubbles on the liquid surface to completely disappear after stirring stops. In Examples 1 and 2, the bubbles were basically eliminated within 3-5 minutes, and no new bubbles were generated during the settling process. Comparative Example 1 had the fastest defoaming speed (<2 minutes), but Comparative Example 2 defoamed more slowly (>8 minutes). The blank sample (without defoamer) showed bubbles that did not disappear for a long time.

[0046] 2. Compatibility and transparency: - Liquid observation: The epoxy mixture containing defoamers from Examples 1 and 2 was clear and transparent, indistinguishable from the blank sample. The mixture containing defoamer from Comparative Example 1 showed a slight opalescence. The mixture containing Comparative Example 2 was essentially transparent.

[0047] - Observation and transmittance testing of cured material: The cured transparent sample (2 mm thick) was tested using a haze meter. The transmittance benchmark for the blank sample was 91%. The transmittance of samples 1 and 2 in Examples 1 and 2 was both >90%, and the visual clarity was excellent. The transmittance of sample 1 in Comparative Example 1 dropped to 85%, and there was slight haziness at the edges. The transmittance of sample 2 in Comparative Example 2 was approximately 88%.

[0048] 3. Surface and mechanical properties: Test the surface energy and tensile shear strength of the cured specimens.

[0049] - The surface energies of Examples 1 and 2 and the blank sample are relatively high (>40 mN / m), while the surface energy of Comparative Example 1 is extremely low (<22 mN / m).

[0050] - The tensile shear strength of Examples 1 and 2 is comparable to that of the blank sample, while the strength of Comparative Example 1 is reduced by about 15%.

[0051] in conclusion The modified polyolefin defoamer provided by this invention, through its ingenious molecular structure of "hydrophobic polyolefin core + epoxy affinity shell", successfully solves the contradiction between compatibility and defoaming efficiency of traditional defoamers in epoxy resins. While achieving high-efficiency defoaming, it perfectly maintains the transparency and final mechanical properties of the system, providing an ideal solution for high-end epoxy applications.

Claims

1. A modified polyolefin defoamer for epoxy resin, characterized in that, The defoamer is a polymer POLX (I) having the general formula (I); wherein, P is a hydrophobic segment of a polyolefin, selected from polyisobutylene, hydrogenated polybutadiene, ethylene-propylene copolymer or propylene-α-olefin copolymer with a number average molecular weight of 800-5000 g / mol; O is a chemical bond or a short chain containing ester group, amide group or urethane group; L is a polyoxyethylene segment, polyoxypropylene segment or copolymer segment of the same, or a C2-C12 alkyl chain containing hydroxyl or carboxyl groups; X is at least one of epoxy group, carboxyl group, acid anhydride group, primary or secondary amine group, hydroxyl group or silaneoxy group.

2. The defoamer according to claim 1, characterized in that, The hydrophobic segment P of the polyolefin is polyisobutylene or hydrogenated polybutadiene with a number average molecular weight of 1000-3000 g / mol.

3. The defoamer according to claim 1, characterized in that, The epoxy affinity functional group X is an epoxy group, an anhydride group, or a silaneoxy group.

4. The defoamer according to claim 1, characterized in that, The defoamer has a number-average molecular weight of 1500-8000 g / mol and a molecular weight distribution of 1.05-1.

50.

5. A method for preparing the defoamer according to any one of claims 1-4, characterized in that, include: The defoamer is obtained by reacting a polyolefin with active groups at one or both ends with a compound containing an epoxy affinity functional group X.

6. A method for preparing the defoamer according to any one of claims 1-4, characterized in that, include: The defoamer is obtained by grafting a monomer containing functional group X onto the polyolefin backbone using free radical grafting or anionic grafting techniques.

7. The use of the modified polyolefin defoamer as described in any one of claims 1-4 in epoxy resin compositions.

8. An epoxy resin composition, characterized in that, It comprises epoxy resin, curing agent, and modified polyolefin defoamer as described in any one of claims 1-4.

9. The epoxy resin composition according to claim 8, characterized in that, The amount of defoamer added is 0.01-2.0 parts by weight per 100 parts by weight of epoxy resin.

10. The epoxy resin composition according to claim 9, characterized in that, The amount of defoamer added is 0.05-0.5 parts by weight.