Fireproof and environment-friendly acrylate adhesive and preparation method thereof

Abstract

The application discloses an acrylate adhesive with fireproof performance and environmental protection and a preparation method thereof, and particularly relates to the technical field of adhesives, which is composed of a two-component system, the first component contains methyl acrylate monomers, epoxy modified acrylate, a toughening agent, peroxide, a stabilizer and a flame retardant, and the second component contains methyl acrylate monomers, epoxy modified acrylate, a toughening agent, an adhesion tackifier, a promoter and a flame retardant. The flame retardant is compounded by phosphorus nitride and phosphorus nitrogen at a ratio of 1:1 and is treated by a silane coupling agent; the stabilizer contains a metal ion chelating agent and an antioxidant. In the preparation, stepwise heating dispersion and low-temperature addition of active components are adopted to ensure storage stability. Under a high flame retardant addition amount, the application still has excellent shear strength, peeling strength and moisture heat aging resistance, has a long storage gel time, has a high flame retardation effect, and solves the problems of mechanical property reduction and storage instability caused by traditional flame retardation modification.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, and more particularly to an acrylic ester adhesive with fireproof performance and environmental protection and a preparation method thereof. BACKGROUND

[0002] Acrylic ester adhesive is a kind of thermosetting structural adhesive with ester monomer containing acrylic acid or methacrylic acid structure group as base material, and with curing agent, initiator and accelerator added to promote rapid curing, so that certain bonding strength and bonding effect can be achieved in a short period. The first generation acrylic ester adhesive (FGA for short) was accidentally discovered by Eastman Company in the United States when a series of vinyl compounds were synthesized in 1955. The adhesive is mainly composed of acrylic monomer, catalyst and elastomer. Although the adhesive has high shear strength, its peel strength, bending and impact strength are low, and the curing speed is slow, so it has not been widely used in the early stage. Researchers added various rubbers for modification to improve the peel strength, and developed the second generation acrylic ester adhesive (SGA for short). The acrylic ester adhesive has the advantages of room temperature rapid curing, no need for strict quantification, good toughness, good fatigue performance, and oil bonding, and occupies an important position in structural adhesive bonding. However, SGA uses methyl methacrylate as the main monomer, which has a low boiling point and a high vapor pressure at room temperature, has a stimulating odor, and can cause numbness to the nervous system of the human body, so that the operating personnel and people who contact the product in the future application will feel uncomfortable. With the gradual enhancement of people's environmental protection consciousness, people's requirements for physical health are also getting higher and higher, and the requirements for working environment are also gradually improving, so the requirement for improving the odor is put forward urgently in the production process of many manufacturers. Therefore, some low odor acrylic ester adhesives have appeared on the market, but these products have not really surpassed methyl methacrylate in performance. Due to the characteristics of the low molecular structure of methyl methacrylate itself, whether it is penetration or infiltration on the surface of the bonded material, it has unique advantages and excellent bonding effect. The low odor acrylic ester adhesives on the market mainly use high molecular aromatic hydrocarbon acrylate or methacrylic acid as the base monomer, so there is a great impact on the bonding effect, especially in the aspect of aging resistance, the performance decline is even faster.

[0003] The invention patent of patent application publication number CN103865405A discloses an environment-friendly aging-resistant acrylate adhesive, which greatly improves the production operation site environment quality, has excellent peeling performance, better shear strength and tensile strength and weather resistance compared with the prior art. However, the formula does not have fireproof performance. If the existing field increases the flame retardant to meet the fireproof requirement, a large amount of flame retardant needs to be added. The large increase of the flame retardant will cause the bonding strength to decrease and the storage stability of the product to become poor and easy to gel. Since the curing system of the acrylate adhesive is similar to the anaerobic adhesive acrylate adhesive system, the existence of active metal ions such as iron ions and copper ions will cause the adhesive to gel and form a lump, which is finally scrapped. The addition of viscosity materials cannot uniformly disperse the flame retardant, thereby causing problems in aging resistance to heat and humidity.

[0004] Therefore, the present application provides an acrylate adhesive with fireproof performance and environmental protection and a preparation method thereof to solve the above problems. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the present application provides an acrylate adhesive with fireproof performance and environmental protection and a preparation method thereof to solve the problems raised in the above background art.

[0006] To achieve the above-mentioned purposes, the present application provides the following technical solutions: an acrylate adhesive with fireproof performance and environmental protection, which is composed of two components, and the volume ratio of the first component and the second component is 1:1 when they are used in mixture. The first component includes the following raw materials in parts by weight:

[0007] methyl acrylate or acrylate combined monomer 40-50 parts, epoxy modified acrylate monomer 10-12 parts, toughening agent 5-6 parts, thickening agent 3-5 parts, peroxide 3-5 parts, stabilizer 1-1.4 parts, flame retardant 20-25 parts;

[0008] The second component includes the following raw materials in parts by weight:

[0009] methyl acrylate or acrylate combined monomer 35-45 parts, epoxy modified acrylate monomer 10-12 parts, toughening agent 5-6 parts, thickening agent 3-5 parts, adhesion tackifier 7-10 parts, promoter composition 16-25 parts, flame retardant 20-25 parts;

[0010] The flame retardant is a compounded system of phosphazene flame retardant and phosphorus-nitrogen flame retardant in a mass ratio of 1:1, and the total addition amount of the flame retardant is 30-50% of the total weight of the adhesive, and the flame retardant is surface treated by a silane coupling agent;

[0011] The stabilizer includes a metal ion chelating agent and an antioxidant.

[0012] The two-component design realizes curing through the reaction of peroxide in the first component and the accelerator in the second component, avoiding the instability problem in single-component storage;

[0013] In the flame retardant compound system, phosphazene has both gas phase flame retardation and carbonization effect, phosphorus-nitrogen type realizes dehydration carbonization and releases inert gas for flame retardation, and phosphazene and phosphorus-nitrogen type realize synergistic effect in a mass ratio of 1:1;

[0014] The silane coupling agent treated flame retardant can improve the compatibility with the organic matrix and reduce agglomeration;

[0015] The metal ion chelating agent captures trace iron and copper ions in the system to avoid their catalysis of acrylate polymerization to cause gelation, and the antioxidant delays oxidative aging.

[0016] Thus, at a high flame retardant addition amount, good shear strength, peeling strength and storage stability are still maintained, the balance of "high flame retardation + high performance" is realized, and the problems of mechanical property decline and storage instability caused by traditional addition of flame retardants are solved.

[0017] The silane coupling agent treated flame retardant matches the hydrophobic surface of hydrophobic fumed white carbon black, reduces agglomeration, and EDTA disodium salt chelates metal ions to avoid trace metal impurities brought by the flame retardant from causing gelation, and the three work together to enable stable storage after high flame retardant addition.

[0018] Preferably, the phosphazene type flame retardant is hexaphenoxycyclotriphosphazene, and the phosphorus-nitrogen type flame retardant is a compound of ammonium polyphosphate (APP) and melamine cyanurate (MCA).

[0019] Hexaphenoxycyclotriphosphazene has high thermal stability, captures gas phase active species containing phosphorus free radicals during combustion, and promotes carbonization; APP generates phosphoric acid by thermal decomposition to catalyze dehydration carbonization, and MCA releases melamine gas to dilute oxygen, and the two compounds strengthen condensed phase flame retardation, form "gas phase + condensed phase" synergy with phosphazene, and compared with single flame retardant, the compound system enables the flame retardation grade to be improved from UL94 V-2 to V-0, and the flame retardant amount can be reduced.

[0020] Preferably, the metal ion chelating agent includes one or more of EDTA disodium salt and tartaric acid, wherein the full name of EDTA disodium salt is ethylenediaminetetraacetic acid disodium salt, and the antioxidant is antioxidant 264.

[0021] EDTA disodium salt and Fe 3+ , Cu 2+The tartaric acid forms a stable chelate with the metal ion through the hydroxyl group, which blocks the catalytic effect of the metal ion on the free radical polymerization of the acrylate, and the antioxidant 264 terminates the oxidation chain reaction by capturing free radicals to inhibit the degradation of the acrylate molecular chain under the action of heat and oxygen. The metal ion chelating agent and the antioxidant in the stabilizer work together to prevent gelation caused by metal ions and enhance the antioxidant property, achieving effects that cannot be achieved by using them alone.

[0022] Preferably, the toughening agent is carboxyl-terminated butyl nitrile rubber (CTBN), and the thickening agent is hydrophobic fumed white carbon black.

[0023] The carboxyl groups of CTBN can react with the epoxy groups of the epoxy-modified acrylate to form chemical cross-linking, forming elastic microzones in the curing system to absorb impact energy; the surface hydroxyl groups of the hydrophobic fumed white carbon black form a three-dimensional network through hydrogen bonds to increase the viscosity of the system and enhance the compatibility with the flame retardant; compared with ordinary butyl nitrile rubber, CTBN can improve the peel strength; and the hydrophobic fumed white carbon black improves the uniformity of the dispersion of the flame retardant.

[0024] Preferably, the peroxide is selected from one or more combinations of hydroperoxide, alkyl peroxide, peroxide ester, diacyl peroxide, or peroxide ketal.

[0025] Preferably, the adhesion promoter is selected from one or more combinations of aliphatic urethane acrylate, aliphatic urethane methacrylate, aliphatic modified urethane acrylate, polyester acrylate, or aromatic urethane acrylate.

[0026] Preferably, the accelerator composition is selected from one or more combinations of N,N-dimethylaniline, N,N-dimethylformamide, N,N-diethylaniline, benzyldimethylamine, triethylamine, thiourea, trimethylthiourea, phenylthiourea, cobalt naphthenate, copper naphthenate, dodecyl mercaptan, butyraldehyde-aniline condensate 808, or butyraldehyde-n-butylamine condensate 833.

[0027] The peroxide methyl ethyl ketone decomposes under the action of the accelerator (amine + thiourea) to generate free radicals, initiating the polymerization of the monomers; the urethane groups of the aliphatic urethane acrylate react with the surface hydroxyl and carboxyl groups of the substrate (such as metal and plastic) to enhance the interfacial adhesion; the amine accelerator accelerates the decomposition of the peroxide, and the thiourea adjusts the curing rate to avoid excessive curing that causes internal stress.

[0028] Preferably, the metal ion chelating agent accounts for 30-50% of the total weight of the stabilizer.

[0029] By adjusting the total weight of the metal ion chelating agent, it is possible to avoid too low a weight that cannot completely chelate the metal ion, and too high a weight that causes insufficient antioxidant and makes the system prone to oxidation and discoloration.

[0030] The application discloses a preparation method of an acrylic ester adhesive with fireproof performance and environmental protection.

[0031] Step 1, preparation of the first component:

[0032] The methyl acrylate monomer, the epoxy modified acrylate monomer and the flame retardant are dispersed at a high speed for 30 minutes at 50-60 DEG C.

[0033] The toughening agent, the thickening agent and the stabilizer are added, and the temperature is increased to 80-90 DEG C for stirring for 2 hours.

[0034] The temperature is decreased to below 40 DEG C, and the peroxide is added.

[0035] Step 2, preparation of the second component:

[0036] The methyl acrylate monomer, the epoxy modified acrylate monomer and the flame retardant are dispersed at a high speed for 30 minutes at 50-60 DEG C.

[0037] The toughening agent, the thickening agent and the adhesion tackifier are added, and the temperature is increased to 80-90 DEG C for stirring for 2 hours.

[0038] The temperature is decreased to below 40 DEG C, and the accelerator composition is added.

[0039] Step 3, the first component and the second component are stored after being divided, and are mixed according to a volume ratio of 1:1 before use.

[0040] In the preparation of the first component, the monomer and the flame retardant are dispersed first, then the toughening agent and the like are added after temperature increase, and the peroxide is added after temperature decrease; the second component is similar, and the accelerator is finally added.

[0041] Through step-by-step temperature increase (dispersion at 50-60 DEG C -> reaction at 80-90 DEG C -> addition of the active component below 40 DEG C), the peroxide / accelerator is prevented from being prematurely reacted at high temperature, and the component storage stability is ensured; high-speed dispersion enables the flame retardant to be uniformly distributed.

[0042] The acrylic ester adhesive with fireproof performance and environmental protection and the preparation method thereof have the following beneficial effects:

[0043] The phosphonitrile and phosphorus-nitrogen flame retardants are compounded according to a ratio of 1:1, and are subjected to surface treatment through a silane coupling agent, so that the adhesive has the effect of self-extinguishing from fire, and the shear strength and the 180 DEG peeling strength are equivalent to those of a traditional product without flame retardant, and the industry problem that high flame retardation and high mechanical performance cannot be simultaneously achieved is solved.

[0044] Trace amounts of iron and copper ions in the system are captured through a metal ion chelating agent, so that the gelation caused by the catalysis of the acrylic ester polymerization is avoided, and in combination with the step-by-step preparation process, the system has a relatively high gelation time under a storage condition of 50 DEG C.

[0045] By improving dispersibility through surface treatment of flame retardant, reducing water penetration channel, and cooperating with synergistic effect of antioxidant 264, rapid aging can be avoided while shear strength can be maintained.

[0046] And the whole formula component does not use toxic and harmful flame-retardant components, and the two-component design can be used as needed, suitable for bonding of various substrates such as metals and plastics, and meets the comprehensive needs of fireproofing, environmental protection and high performance in the fields of building and electronics. DETAILED DESCRIPTION

[0047] All other embodiments obtained by those of ordinary skill in the art without creative labor based on the embodiments in the present application belong to the scope of protection of the present application.

[0048] Example 1

[0049] First component: 40 parts of methyl methacrylate, 10 parts of epoxy modified acrylate, 5 parts of CTBN, 3 parts of hydrophobic fumed white carbon black, 3 parts of methyl ethyl ketone peroxide, 0.3 parts of EDTA disodium salt, 0.7 parts of antioxidant 264, 20 parts of hexaphenoxy cyclotriphosphazene.

[0050] Second component: 35 parts of methyl methacrylate, 10 parts of epoxy modified acrylate, 5 parts of CTBN, 3 parts of hydrophobic fumed white carbon black, 7 parts of aliphatic polyurethane acrylate, 8 parts of N,N-dimethyl aniline, 8 parts of thiourea, 20 parts of polyammonium phosphate (APP) and melamine cyanurate (MCA) compounded in a mass ratio of 2:1.

[0051] Step 1, preparation of the first component:

[0052] The methyl methacrylate monomer, epoxy modified acrylate monomer and flame retardant treated with silane coupling agent KH550 are dispersed at 50℃ for 30 minutes at high speed;

[0053] Add toughening agent, thickening agent and stabilizer, and stir at 80℃ for 2 hours;

[0054] Cool down to below 40℃, add peroxide, and store after preparation;

[0055] Step 2, preparation of the second component:

[0056] The methyl methacrylate monomer, epoxy modified acrylate monomer and flame retardant treated with silane coupling agent KH550 are dispersed at 50℃ for 30 minutes at high speed;

[0057] Add toughening agent, thickening agent and adhesion tackifier, and stir at 80℃ for 2 hours;

[0058] Cool down to below 40℃, add accelerator composition, and store after preparation.

[0059] Example 2

[0060] First component: octadecyl acrylate 50 parts, epoxy modified acrylate 12 parts, CTBN 6 parts, hydrophobic fumed white carbon black 5 parts, peroxide methyl ethyl ketone 5 parts, tartaric acid 0.7 parts, 0.7 parts of antioxidant 264, hexaphenoxycyclotriphosphazene 25 parts.

[0061] Second component: octadecyl acrylate 45 parts, epoxy modified acrylate 12 parts, CTBN 6 parts, hydrophobic fumed white carbon black 5 parts, aliphatic polyurethane acrylate 10 parts, N,N-dimethyl aniline 15 parts + thiourea 10 parts, ammonium polyphosphate (APP) and melamine cyanurate (MCA) 25 parts compounded in a mass ratio of 2:1.

[0062] Preparation method same as example 1.

[0063] Comparative example 1

[0064] The formula is the same as example 1, and the stabilizer only contains 1 part of antioxidant 264, without EDTA disodium salt.

[0065] Comparative example 2

[0066] The formula is the same as example 1, and the flame retardant is not treated with silane coupling agent.

[0067] Comparative example 3

[0068] The formula is the same as example 1, and the flame retardant only uses hexaphenoxycyclotriphosphazene (40 parts), without ammonium polyphosphate (APP) and melamine cyanurate (MCA).

[0069] Comparative example 4

[0070] The formula component of an environmentally friendly aging-resistant acrylate adhesive disclosed in prior art Chinese patent publication No. CN103865405A (without flame retardant, without metal ion chelating agent).

[0071] The products prepared in the above examples 1-2 and comparative examples 1-4 are tested as follows, and the test results are shown in Table 1.

[0072] Test method

[0073] Shear strength: according to GB / T7124-2008, test aluminum alloy-aluminum alloy bonding piece (25mm x 100mm), rate 10mm / min.

[0074] 180°peeling strength: according to GB / T2790-1995, test aluminum foil-polypropylene bonding piece (25mm wide), rate 300mm / min.

[0075] Flame Retardant Performance: According to UL94 standard, the vertical burning grade and the self-extinguishing time after leaving the fire of 1.6mm thick sample were tested.

[0076] Storage Stability: The time of first gel appearance was recorded under constant temperature storage at 50℃.

[0077] Wet Heat Aging Resistance: The shear strength retention rate (strength after aging / initial strength x 100%) was tested after 60 days of storage under the condition of temperature 85℃ / 85% humidity.

[0078] Table 1: Test data table

[0079] Index Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Shear strength (MPa) 18.2 17.5 17.8 15.3 16.0 16.5 180° peeling strength (N / 25mm) 85 82 83 68 75 80 Flame retardant rating (UL94) V-0 V-0 V-0 V-1 V-2 Not flame retardant Fire separation self-extinguishing time (s) 3 2 3 8 15 >30 Gel time at 50℃ (days) 35 32 8 33 40 Retention rate after hydrothermal aging (%) 88 86 85 70 80 82

[0080] From the above table, in terms of mechanical properties: the shear strength (17.5-18.2MPa) and the peeling strength (82-85N / 25mm) of examples 1 and 2 are comparable to those of comparative example 4 (traditional product without flame retardant), which shows that the present application still maintains excellent mechanical properties after adding 30-50% flame retardant, solving the problem of performance degradation caused by traditional addition of flame retardant, which benefits from the synergistic toughening of surface treatment of flame retardant (improving compatibility) and toughener-epoxy monomer.

[0081] In terms of flame retardant performance: examples 1 and 2 both reach UL94 V-0 level, and the self-extinguishing time after leaving the fire is less than 3s; comparative example 3 (single component flame retardant) is only V-2 level, and the self-extinguishing time is 15s, which proves the synergistic effect of phosphazene / phosphorus-nitrogen complex; comparative example 2 (flame retardant without treatment) reduces to V-1 level due to uneven dispersion, which shows the key role of surface treatment on flame retardant performance.

[0082] In terms of storage stability: the gel time of examples 1 and 2 under 50℃ storage is 32-35 days, and that of comparative example 1 (without metal ion chelating agent) is only 8 days, which verifies the necessity of metal ion chelating agent for inhibiting gel; although the traditional product (comparative example 4) is storage stable, it has no flame retardant property and cannot meet the fireproof requirement.

[0083] In terms of wet heat aging resistance: the retention rate (86-88%) of examples 1 and 2 is higher than that of comparative example 2 (70%), because the treated flame retardant is uniformly dispersed, reducing the water penetration channel; it is close to that of comparative example 4 (82%), which shows that the present application does not reduce the aging resistance after adding flame retardant, benefiting from the synergistic effect of antioxidant and flame retardant.

[0084] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A fire-resistant and environmentally friendly acrylic adhesive, consisting of two components, wherein the volume ratio of the first component to the second component when mixed is 1:1, characterized in that: The first component includes the following raw materials in parts by weight: 40-50 parts of methacrylate or acrylate combination monomer, 10-12 parts of epoxy modified acrylate monomer, 5-6 parts of toughening agent, 3-5 parts of thickener, 3-5 parts of peroxide, 1-1.4 parts of stabilizer, 20-25 parts of flame retardant; The second component includes the following raw materials in parts by weight: 35-45 parts of methacrylate or acrylate combination monomer, 10-12 parts of epoxy modified acrylate monomer, 5-6 parts of toughening agent, 3-5 parts of thickener, 7-10 parts of adhesion promoter, 16-25 parts of accelerator composition, and 20-25 parts of flame retardant; The flame retardant is a compound system of a phosphazene flame retardant and a phosphorus nitrogen flame retardant in a mass ratio of 1:1, the total addition amount of the flame retardant is 30-50% of the total weight of the adhesive, and the flame retardant is surface treated with a silane coupling agent; The stabilizer includes a metal ion chelating agent and an antioxidant.

2. The fire-resistant and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The phosphazene flame retardant is hexaphenoxy cyclotriphosphazene, and the phosphorus-nitrogen flame retardant is a compound of ammonium polyphosphate and melamine cyanurate.

3. The fireproof and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The metal ion chelating agent includes one or more of EDTA disodium salt and tartaric acid.

4. The fire-resistant and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The antioxidant is antioxidant 264.

5. The fire-resistant and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The toughening agent is carboxyl-terminated nitrile rubber, and the thickening agent is hydrophobic fumed silica.

6. The fireproof and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The peroxide is selected from one or more of hydroperoxide, alkyl peroxide, peroxyester, diacyl peroxide or peroxyketal.

7. The fireproof and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The adhesion tackifier is selected from one or more of aliphatic polyurethane acrylate, aliphatic polyurethane methacrylate, aliphatic modified polyurethane acrylate, polyester acrylate or aromatic polyurethane acrylate.

8. The fireproof and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The accelerator composition is selected from one or more of N,N-dimethylaniline, N,N-dimethylformamide, N,N-diethylaniline, benzyldimethylamine, triethylamine, thiourea, trimethylthiourea, phenylthiourea, cobalt naphthenate, copper naphthenate, dodecyl mercaptan, butyraldehyde-aniline condensate 808 or butyraldehyde-n-butylamine condensate 833.

9. The fireproof and environmentally friendly acrylic adhesive according to claim 1, characterized in that: The metal ion chelating agent accounts for 30 to 50% of the total weight of the stabilizer.

10. A method for preparing a fire-resistant and environmentally friendly acrylic adhesive according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: Preparation of the first component: Disperse methacrylate monomer, epoxy-modified acrylate monomer and flame retardant at high speed at 50-60°C for 30 minutes; Add toughening agent, thickener and stabilizer, raise the temperature to 80-90℃ and stir for 2 hours; Cool down to below 40℃ and add peroxide; Step 2: Preparation of the second component: Disperse methacrylate monomer, epoxy-modified acrylate monomer and flame retardant at high speed at 50-60°C for 30 minutes; Add toughening agent, thickener, and adhesion tackifier, raise the temperature to 80-90°C and stir for 2 hours; Cooling to below 40°C and adding the accelerator composition; Step 3: Store the first and second components separately and mix them in a 1:1 volume ratio before use.