Electron beam-moisture dual-curing hot melt adhesive, preparation method and application

Abstract

The invention discloses an electron beam-moisture dual-curing hot melt adhesive, belongs to the technical field of adhesives, and solves the problems that the construction melting temperature of an existing conventional PUR reactive hot melt adhesive is relatively high and needs to reach 150 DEG C or above; in order to solve the technical problems that glue after coating needs to be maintained at normal temperature or 60 DEG C for 24-72 hours to reach ideal strength, and the production efficiency is low, the polyurethane adhesive is prepared by compounding the following substances: diisocyanate, polyether polyol, hydroxypropyl acrylate, hydroxyethyl acrylate and a drier. The weight of the acrylic acid, the vinyl pyrrolidone, the isobornyl acrylate, the acryloyl morpholine, the tackifier and the like is 40-60% of the total weight of the raw materials; the EB device is more flexible to mount and can be irradiated horizontally or vertically downwards, so that various radiation transmission devices can be mounted, and radiation processing and production are facilitated; the EB device is free of radioactive substance residues, is an environment-friendly and clean radiation source and is beneficial to safe production.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and in particular relates to an electron beam-moisture dual-curing hot melt adhesive, a preparation method and an application thereof. Background Art

[0002] Reactive hot melt adhesive (PUR) is heated and melted into a fluid under the condition of inhibiting chemical reaction for easy coating; after the two adherends are bonded and cooled, the adhesive layer condenses to play a bonding role; then, with the help of moisture in the air and moisture attached to the surface of the adherend, it reacts with it and extends the chain to generate a high molecular polymer with high cohesion, which significantly improves the adhesion, heat resistance, and low temperature resistance. Due to its extremely high reactivity, it shows excellent adhesion to a variety of materials and is widely used in the bonding of washing machine top covers, disinfection cabinet top covers, book binding, car lights, furniture edge banding, shoemaking, etc.; the conventional PUR reactive hot melt adhesive has a high melting temperature during construction, which needs to reach 150°C or above; the glue after coating needs to be cured at room temperature or 60°C for 24h to 72h to achieve the ideal strength, and the production efficiency is low; therefore, UV polyurethane reactive hot melt adhesive was introduced, which uses the characteristics of UV light curing to accelerate the curing process through ultraviolet light, which is particularly suitable for scenes that require fast curing and high bonding strength;

[0003] Existing UV polyurethane reactive hot melt adhesives must have a photoinitiator to quickly form wet strength before they can be cured. Most photoinitiators are organic compounds containing benzoyl groups, which are harmful to human health. They are also low-molecular-weight organic substances. After UV curing, a lot of photoinitiators that did not participate in the curing initiation still remain in the cured coating and are prone to migration. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an electron beam-moisture dual-curing hot melt adhesive, a preparation method and an application thereof, and provides a polyurethane resin OCN-RN-COO-ROR′-OOC-NRN-COO-R-CH=CH2 having an isocyanate group and a C=C double bond on the side chain. By using the polyurethane resin and a composition thereof, an electron beam-moisture dual-curing hot melt adhesive with low viscosity, short setting time and the ability to quickly form wet strength is obtained.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A polyurethane resin is prepared from the following materials in parts by weight: 10-20 parts of diisocyanate, 60-80 parts of polyether polyol, 2-5 parts of hydroxypropyl acrylate or 2-5 parts of hydroxyethyl acrylate, and 0.05-0.1 parts of a drying agent.

[0007] Preferably, the diisocyanate is selected from aliphatic, aromatic and alicyclic diisocyanates.

[0008] Preferably, the aromatic diisocyanate is selected from one or more of 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate and a mixture of 2,6-toluene diisocyanate;

[0009] The aliphatic diisocyanate is selected from one or more of 1,4-butylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,10-decamethylene diisocyanate, 2-butyl-2-ethylpentamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate;

[0010] The alicyclic diisocyanate is selected from one or more of isophorone diisocyanate, 2-isocyanatopropylcyclohexyl isocyanate, 2,4'-methylene di(cyclohexyl) diisocyanate and 4-methylcyclohexane-1,3-diisocyanate.

[0011] Preferably, the polyether polyol is polyether diol.

[0012] Preferably, the drying agent is dibutyltin dilaurate.

[0013] An electron beam-moisture dual-curing hot melt adhesive comprises 40 to 60 parts by weight of a polyurethane resin, 10 to 40 parts by weight of a tackifier, 2 to 6 parts by weight of acrylic acid, and 5 to 10 parts by weight of one or more of vinyl pyrrolidone, isobornyl acrylate, and acryloyl morpholine.

[0014] Preferably, the tackifier is selected from one of natural resin, phenolic resin and polyacrylate.

[0015] Preferably, the functionality of the polyacrylate is ≤2, and the content of C1-C8 alkyl (meth)acrylate in the polyacrylate is ≥80%.

[0016] Weight average molecular weight <30000Da.

[0017] A method for preparing an electron beam-moisture dual-curing hot melt adhesive, which is used to prepare the above-mentioned electron beam-moisture dual-curing hot melt adhesive, comprises the following steps:

[0018] Step 1: adding diisocyanate and a drier into a reaction container and mixing them to obtain a mixture A;

[0019] Step 2: Add polyether polyol to mixture A, control the reaction temperature to 60-80° C., react for 2-4 hours, and obtain polyether chain-extended diisocyanate;

[0020] Step 3: adding one of hydroxypropyl acrylate and hydroxyethyl acrylate to the polyether chain-extended diisocyanate and reacting for 2 to 4 hours to obtain a polyurethane resin containing a C=C double bond and a diisocyanate group;

[0021] Step 4: Evenly mix the polyurethane resin containing C=C double bonds and diisocyanate groups with a tackifier, acrylic acid and vinyl pyrrolidone to obtain an electron beam-moisture dual-curing hot melt adhesive.

[0022] An application of an electron beam-moisture dual-curing hot melt adhesive, using the above-mentioned electron beam-moisture dual-curing hot melt adhesive to bond and cure polymer films, paper, metal foil, thin wood boards, fiber nonwovens made of natural synthetic fibers and shaped solid products.

[0023] Preferably, it is used for bonding polymer films.

[0024] Preferably, the application amount of the hot melt adhesive is 20 to 80 g / m2.

[0025] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0026] 1. Provided is a polyurethane resin having an isocyanate group and a C=C double bond on the side chain. This resin and other compositions can be used to form a polyurethane reactive hot melt adhesive (electron beam-moisture dual-curing hot melt adhesive) that can be dual-cured by electron beam (EB) and moisture to form a polyurethane reactive hot melt adhesive with low viscosity, short setting time and rapid wet strength formation. The performance of this polyurethane reactive hot melt adhesive is superior to that of traditional PUR hot melt adhesive and UV polyurethane reactive hot melt adhesive. Without using a photoinitiator, it can quickly achieve initial bonding strength and moisture-cured tight bonding strength, and significantly improves peel strength.

[0027] 2. Diisocyanate is one of the key raw materials in the synthesis of polyurethane resin. It provides NCO groups and reacts with hydroxyl groups in polyether polyols to form urethane bonds. It is the basis for building polyurethane molecular chains. During the curing process of the glue, the NCO groups can react with hydroxyl groups and further cross-link to form a three-dimensional network structure, thereby achieving curing;

[0028] As another main raw material of polyurethane resin, polyether polyol contains multiple hydroxyl groups and reacts with diisocyanate to form polyurethane segments. The molecular weight and functionality of polyether polyol affect the properties of polyurethane resin, such as flexibility and mechanical strength.

[0029] Hydroxypropyl acrylate and hydroxyethyl acrylate are functional monomers that introduce C=C double bonds, which can undergo polymerization during EB curing to increase the crosslinking density, improve the curing speed and the performance of the final product. The hydroxyl groups of hydroxypropyl acrylate and hydroxyethyl acrylate can also react with isocyanate to increase the interaction between molecules.

[0030] 3. EB curing does not require the addition of initiators or catalysts, so the polymers generated by EB radiation polymerization are purer than UV and have no additive residues; the high-energy electron beam generated by the accelerator bombards the heavy metal target to generate X-rays, which have significantly stronger penetrating power than UV light curing and can achieve the processing of thicker products; the irradiation processing using an accelerator is more efficient, and the EB energy is about 20,000 times that of UV energy, and the processing can be completed in a shorter time (usually irradiation time is measured in seconds or minutes); the EB device is more flexible to install, and can be irradiated horizontally or vertically downward, so various types of radiation transmission devices can be installed to facilitate radiation processing and production; the EB device has no residual radioactive substances, is an environmentally friendly, "clean" radiation source, and is conducive to safe production. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0032] In Examples 1 to 5, the polyurethane resin was prepared by the following steps; the selection and weight ratio of each substance were as shown in Table 1.

[0033] Step 1: Mix diisocyanate and a drier to obtain a mixture A;

[0034] Step 2: Add polyether polyol to mixture A, control the reaction temperature to 70° C., and react for 3 hours to obtain polyether chain-extended diisocyanate;

[0035] Step 3: adding one of hydroxypropyl acrylate and hydroxyethyl acrylate to the polyether chain-extended diisocyanate and reacting for 3 hours to obtain a polyurethane resin containing a C=C double bond and a diisocyanate group;

[0036] Preparation of electron beam-moisture dual-cure hot melt adhesive:

[0037] The polyurethane resin containing C=C double bonds and diisocyanate groups is uniformly mixed with a tackifier, acrylic acid and vinyl pyrrolidone to obtain an electron beam-moisture dual-curing hot melt adhesive.

[0038] Table 1: Types and weight ratios of various substances added in Examples 1 to 5

[0039]

[0040] Table 2: The molar ratio of NCO to OH and the ratio of double bonds to NCO in the final macromolecular groups of the electron beam-moisture dual-curing hot melt adhesive prepared in Examples 1 to 5

[0041] Add Scale Example 1 Example 2 Example 3 Example 4 Example 5 NCO:OH 2:1 2:1 2:1 2:1 2:1 Double bond: NCO 1:1 1:1 1:1 1:2 1:3

[0042] The bonding strength of the electron beam-moisture dual-curing hot melt adhesive on the PET film (polymer film) / tinplate is tested according to the above method, and the measured data are shown in Table 3. The PET film is purchased from 5c PET film of Dongcai. The above polyurethane adhesive composition is applied to the tinplate at 90-120°C, and the tinplate coated with the hot melt adhesive is contacted and compounded with the coated or uncoated PET film. The adhesive application amount is 40g / ㎡, and the two substrates are cured by EB and moisture after contacting each other.

[0043] Table 3: Bonding strength data of electron beam-moisture dual-curing hot melt adhesive on PET film (polymer film) / tinplate

[0044]

[0045] The viscosity of the electron beam-moisture dual-curing hot melt adhesive of the present invention is measured at 90° C., and the viscosity may be less than 10 Pas.

[0046] The electron beam-moisture dual-curing hot melt adhesive EB used in the present invention can form a good initial bonding strength immediately after irradiation, and the bonding strength will gradually increase in the later stage, and the final strength can be formed after 24h to 72h at room temperature.

[0047] This application reserves some NCO in the grafting reaction, so that the final macromolecule has two active groups, double bond and NCO. As a result, the 2,4-toluene diisocyanate molecule has a relatively rigid benzene ring, and in the same macromolecular segment, it has better tensile strength; the greater the amount of diisocyanate added, the higher the NCO content, the lower the initial viscosity of the glue, and the later glue is harder and has lower fastness. The smaller the amount of diisocyanate added, the lower the NCO content, and the synthetic reaction and glue strength will be affected.

[0048] The polyether diol plays the role of expanding the molecular chain segment of diisocyanate so that it does not produce violent polymerization when grafting double bond groups (if violent polymerization occurs, the synthesis can no longer proceed), and the linear structure of the polyether molecule can increase the flexibility and viscoelasticity of the glue.

[0049] The double bonds in hydroxypropyl acrylate greatly shorten the coagulation time in the glue system. After the glue is cured by EB, the double bonds will produce free radical reactions and eventually form high molecular polymers. This curing process can be completed in an instant, so that the electron beam-moisture dual-curing hot melt adhesive recorded in the present invention can quickly form initial bonding force.

[0050] Polyether diol is a dihydroxy-terminated oligomer, and hydroxypropyl acrylate is a monohydroxy-terminated unsaturated monomer. These two substances can be effectively linked together to form a macromolecular polymer through the NCO in the diisocyanate.

[0051] It should be noted that:

[0052] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A polyurethane resin, characterized in that The preparation method is prepared by using the following materials in parts by weight: 10-20 parts of diisocyanate, 60-80 parts of polyether polyol, 2-5 parts of hydroxypropyl acrylate or 2-5 parts of hydroxyethyl acrylate, and 0.05-0.1 parts of a drying agent.

2. A polyurethane resin according to claim 1, characterized in that: The diisocyanate is selected from aliphatic, aromatic and alicyclic diisocyanates.

3. A polyurethane resin according to claim 2, characterized in that: The aromatic diisocyanate is selected from one or more of 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate and a mixture of 2,6-toluene diisocyanate; The aliphatic diisocyanate is selected from one or more of 1,4-butylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,10-decamethylene diisocyanate, 2-butyl-2-ethylpentamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; The alicyclic diisocyanate is selected from one or more of isophorone diisocyanate, 2-isocyanatopropylcyclohexyl isocyanate, 2,4'-methylene di(cyclohexyl) diisocyanate and 4-methylcyclohexane-1,3-diisocyanate.

4. The polyurethane resin according to claim 1, characterized in that: The polyether polyol is polyether diol.

5. The polyurethane resin according to claim 1, characterized in that: The drying agent is dibutyltin dilaurate.

6. An electron beam-moisture dual curing hot melt adhesive, characterized in that: According to parts by weight, 40 to 60 parts of a polyurethane resin as described in claims 1 to 5 are used, and 10 to 40 parts of a tackifier, 2 to 6 parts of acrylic acid, 5 to 10 parts of one or more of vinyl pyrrolidone, isobornyl acrylate, and acryloyl morpholine are also included.

7. The electron beam-moisture dual curing hot melt adhesive according to claim 1, characterized in that: The tackifier is selected from one of natural resin, phenolic resin and polyacrylate.

8. A method for preparing an electron beam-moisture dual-curing hot melt adhesive, characterized in that: The method for preparing an electron beam-moisture dual-curing hot melt adhesive as claimed in claims 6 to 7 comprises the following steps: Step 1: Mix diisocyanate and a drier to obtain a mixture A; Step 2: Add polyether polyol to mixture A, control the reaction temperature to 60-80° C., react for 2-4 hours, and obtain polyether chain-extended diisocyanate; Step 3: adding one of hydroxypropyl acrylate and hydroxyethyl acrylate to the polyether chain-extended diisocyanate and reacting for 2 to 4 hours to obtain a polyurethane resin containing a C=C double bond and a diisocyanate group; Step 4: Evenly mix the polyurethane resin containing C=C double bonds and diisocyanate groups with a tackifier, acrylic acid and vinyl pyrrolidone to obtain an electron beam-moisture dual-curing hot melt adhesive.

9. An application of an electron beam-moisture dual curing hot melt adhesive, characterized in that: The electron beam-moisture dual-curing hot melt adhesive described in claims 1 to 4 is used for bonding and curing polymer films, paper, metal foil, thin wood boards, fiber nonwovens made of natural synthetic fibers and shaped solid products.

10. The use of an electron beam-moisture dual curing hot melt adhesive according to claim 6, characterized in that: It is preferably used for bonding polymer films.

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