KR102094329B1 - Structural adhesives with excellent flame retardancy - Google Patents

Abstract

Disclosed is a structural adhesive excellent in flame retardancy.
Structural adhesive according to the present invention is 1 to 20 parts by weight of a reactive diluent containing an epoxy group, 20 to 40 parts by weight of an acid anhydride-based compound, curing accelerator containing an imidazole derivative, based on 100 parts by weight of a bisphenol-based epoxy resin Among 15 parts by weight, 10 to 20 parts by weight of silica particles surface-treated with the first silane, 1 to 20 parts by weight of Halloysite NanoTube (HNT) surface-treated with the second silane, and silicon-based antifoaming agent and silicon-based leveling agent It characterized in that it contains 0.1 to 2 parts by weight of additives containing one or more.

Description

Structural ADHESIVES WITH EXCELLENT FLAME RETARDANCY

The present invention relates to a structural adhesive, and more particularly, to a structural adhesive having excellent flame retardancy, including HNT.

Structural adhesives can be defined as materials used to bond other high strength materials such as wood, composites or metals. Structural adhesives can be used in a variety of applications, such as the automotive and aerospace industries. It can also be used to replace or reinforce conventional fastening techniques such as screws, bolts, nails, staples, and soldering.

Structural adhesives are organic and can burn when exposed to sufficiently high temperatures in the presence of oxygen. Since the structural adhesive is mainly burned in the welding step, it is desirable to increase the resistance to ignition through improvement of the structural adhesive. In addition, in order to be suitable as a structural adhesive, it must have high mechanical strength and impact resistance.

Meanwhile, research has been conducted on structural adhesives containing alumina trihydrate, which is a flame retardant. However, in order for the function of the structural adhesive to effectively function at high temperatures generated during the HFDC welding process, a very high concentration of alumina trihydrate is required. It is also known that high concentrations of alumina trihydrate interfere with the welding process.

Accordingly, there is a need to develop a structural adhesive excellent in flame retardancy, mechanical strength and impact resistance.

Background art related to the present invention includes Republic of Korea Patent Publication No. 10-2017-0127472 (published on November 21, 2017), the document discloses a two-part structural adhesive.

An object of the present invention is to provide a structural adhesive having excellent flame retardancy.

Structural adhesive according to the present invention for achieving the above one object is 1 to 20 parts by weight of a reactive diluent containing an epoxy group, 20 to 40 parts by weight of an acid anhydride-based compound, imidazole-based with respect to 100 parts by weight of bisphenol-based epoxy resin 1 to 15 parts by weight of a curing accelerator containing a derivative, 10 to 20 parts by weight of silica particles surface-treated with a first silane, 1 to 20 parts by weight of Halloysite NanoTube (HNT), surface-treated with a second silane, And 0.1 to 2 parts by weight of an additive containing at least one of a silicone-based antifoaming agent and a silicone-based leveling agent.

The acid anhydride-based compound may include one or more of Hexahydro phthalic anhydride (HHPA), Methyl hexahydro phthalic anhydride (MeHHPA), Tetra hydro phthalic anhydride (THPA) and Methyl tetrahydro phthalic anhydride (MeTHPA).

The silica particles surface-treated with the first silane may have a diameter of 1 to 20 μm.

Each of the first silane and the second silane is 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldime It may include at least one of methoxysilane and 3-chloropropyl trimethoxysilane.

The structural adhesive may further include 0.1 to 1 part by weight of a catalyst.

The structural adhesive according to the present invention can exhibit excellent flame retardancy and mechanical strength by including silica particles that give strength to the epoxy resin and HNT that gives flame retardancy.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and the ordinary knowledge in the technical field to which the present invention pertains. It is provided to fully inform the holder of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Hereinafter, a structural adhesive having excellent flame retardancy according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Structural adhesives according to the present invention are materials used to bond other high strength materials such as wood, composites or metals.

Structural adhesive according to the present invention is 1 to 20 parts by weight of a reactive diluent containing an epoxy group, 20 to 40 parts by weight of an acid anhydride-based compound, curing accelerator containing an imidazole derivative, based on 100 parts by weight of a bisphenol-based epoxy resin Among 15 parts by weight, 10 to 20 parts by weight of silica particles surface-treated with the first silane, 1 to 20 parts by weight of Halloysite NanoTube (HNT) surface-treated with the second silane, and silicon-based antifoaming agent and silicon-based leveling agent It contains 0.1 to 2 parts by weight of additives containing one or more.

The bisphenol-based epoxy resin exists as a liquid at room temperature, and has excellent water resistance, adhesion, and the like. Examples include bisphenol A-type epoxy resins or bisphenol F-type epoxy resins. The equivalent of the bisphenol-based epoxy resin may be 170 to 180 g / eq, but is not limited thereto.

The reactive diluent collectively refers to a substance that lowers the viscosity of the structural adhesive while maintaining excellent properties of the epoxy resin, and preferably includes a bifunctional epoxy group in the form of a fatty glycidyl ether.

It is preferable that the structural adhesive contains 1 to 20 parts by weight of a reactive diluent containing an epoxy group. When the content is less than 1 part by weight, the viscosity of the adhesive and the glass transition temperature may be increased. Conversely, when the content exceeds 20 parts by weight, the viscosity of the adhesive and the glass transition temperature may be reduced.

The acid anhydride-based compound is an alicyclic acid anhydride (Cyclo Aliphatic), and acts as a curing agent. For example, it may include one or more of Hexahydro phthalic anhydride (HHPA), Methyl hexahydro phthalic anhydride (MeHHPA), Tetra hydro phthalic anhydride (THPA) and Methyl tetrahydro phthalic anhydride (MeTHPA).

HHPA is a solid at room temperature, has colorless transparency, and has weather-resistant characteristics. MeHHPA is a liquid at room temperature and has weather resistance and low viscosity. THPA is a solid at room temperature and has excellent workability. MeTHPA is liquid at room temperature and is used for impregnation and lamination.

It is preferable that the structural adhesive contains 20 to 40 parts by weight of an acid anhydride-based compound. If it is less than 20 parts by weight, or more than 40 parts by weight, viscosity control of the structural adhesive may be difficult.

The curing accelerator comprising the imidazole derivative is intended to maintain curing reactivity and storage stability at room temperature ± 20 ° C. It is preferable that the structural adhesive contains 1 to 15 parts by weight of the curing accelerator. If the content is less than 1 part by weight, the effect of the curing accelerator may be insufficient, and when it exceeds 15 parts by weight, there is a problem that only the manufacturing cost increases without effect.

The curing accelerator comprising the imidazole derivative may include one or more of imidazole, isoimidazole, 2-methyl imidazole, 2-ethyl-4-methylimidazole, and the like.

The silica particles surface-treated with the first silane can improve the physical strength of the structural adhesive. Here, the first silane is 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane and 3- Chloropropyl trimethoxysilane.

In addition, the silica particles surface-treated with the first silane may have a diameter of 1 to 20 μm. When the diameter of the silica particles is less than 1 μm, the phenomenon that the particles agglomerate occurs, and when it exceeds 20 μm, the diameter may become too large, thereby deteriorating the surface roughness and workability of the adhesive.

It is preferable that the structural adhesive contains 10 to 20 parts by weight of silica particles surface-treated with the first silane. If it is outside this range, mechanical properties may deteriorate.

The halosite nanotube is an aluminum silicate clay mineral composed of a 1: 1 ratio of aluminum and silicon, and is formed of nanoparticles in a tube shape. The halosite nanotube has excellent dispersibility in the adhesive and imparts flame retardancy.

The halosite nanotubes may be surface treated with a second silane to further improve compatibility and interfacial adhesion in the adhesive.

The length of the halosite nanotube may be 50 to 1000 μm, but is not limited thereto.

The second silane is as described above in the first silane.

The manufacturing method of the halosite nanotubes surface-treated with the second silane is as follows.

First, the halosite nanotube and the organic solvent are mixed at room temperature ± 10 ° C.

The organic solvent is a solvent containing a hydroxy group, and examples thereof include acetone, methanol or ethanol. The hydroxy group of the organic solvent reacts with a silane (Si _n H _{2n + 2} ) coupling agent to form silanol (H ₂ SiOH) by hydrolysis with moisture. The silanol is partially dehydrated and condensed, and accordingly, silane (SiH ₄ ) is adsorbed on the surface of the halosite nanotube.

The halosite nanotubes and the organic solvent may be mixed in a weight ratio of 1: 1 to 1: 3. If it is outside this range, it may be difficult to sufficiently perform the surface treatment of the nanotube.

Next, a silane coupling agent is added to the prepared result and stirred. At this time, the stirring may be performed for approximately 10 to 14 hours so that the nanotube, the solvent, and the silane-based coupling agent can be appropriately mixed, and the organic solvent may be partially removed.

Silane-based coupling agents have a greater effect of reducing oil absorption than other coupling agents such as chromium-based. Accordingly, in the case of surface treatment with a silane-based coupling agent, the interfacial adhesion and dispersibility between components in the adhesive is increased, thereby improving the physical properties of the adhesive.

The silane coupling agent may be added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the halosite nanotube. After stirring, it can be dried at approximately 90 to 100 ° C. for 3 to 5 hours to completely remove the remaining organic solvent.

The silica particles surface-treated with the first silane may likewise be produced using silica particles instead of halosite nanotubes.

It is preferable that the structural adhesive contains 1 to 20 parts by weight of the halosite nanotubes surface-treated with the second silane. If it is outside this range, it is difficult to expect the flame retardant effect of the adhesive.

The additive contains at least one of a silicone-based antifoaming agent and a silicone-based leveling agent, and may include 0.1 to 2 parts by weight. If the content of the additive is less than 0.1 parts by weight, or more than 2 parts by weight, it may be difficult to further improve the required physical properties of the adhesive.

The structural adhesive may further include 0.1 to 1 part by weight of a catalyst to promote the reaction between components in the adhesive.

As the catalyst, an aliphatic urea compound can be used. For example, p-chloro-N, N-dimethyl (Monuron), 3-phenyl-1,1-dimethylurea (Phenuron), 3,4-dichlorophenyl-Ν , Ν-dimethyl (Diuron), N- (3-chloro-4-methylphenyl)-

N ', N'-dimethylurea (Chlortoluron), tert-acrylic- or alkylene amines such as benzyldimethylamine, 2,4,6-tris (dimethylaminomethyl) phenol, pipery Dean or derivatives thereof.

In addition, the structural adhesive of the present invention may further include 0.1 to 3 parts by weight of tetrabutylphosphonium tetrafluoroborate. When the tetrabutylphosphonium tetrafluoroborate is further included, viscosity control is easy, and excellent mechanical properties may be exhibited.

As described above, the structural adhesive according to the present invention may impart strength and flame retardancy by adding silica particles surface-treated with a first silane and HNT surface-treated with a second silane to a bisphenol-based epoxy resin.

In addition, the structural adhesive according to the present invention is a one-component type containing a curing agent that is an acid anhydride-based compound, and there is no need to stir a separate curing agent.

Looking at the specific embodiment of the structural adhesive having excellent flame retardancy as follows.

1. Preparation of structural adhesives with excellent flame retardancy

Examples 1 to 3, and Comparative Examples 1 to 5

Bisphenol A-type epoxy resin (Huntsman), a reactive diluent, a fatty glycidyl ether type bifunctional epoxy group (Shin-Nihon Rika KK), THPA (Sigma Aldrich), 3-chloropropyl trimethoxysilane HNT surface treated with silica (average diameter 10㎛, Sigma Aldrich), silicone antifoaming agent, silicone leveling agent (LG Chemical), curing accelerator 2-methyl imidazole (Sigma Aldrich), 3-chloropropyl trimethoxysilane A structural adhesive was prepared by mixing with the composition of 1.

The composition of Table 1 and Table 2 describes parts by weight based on 100 parts by weight of bisphenol A-type epoxy resin.

Example 4 and Example 5

A structural adhesive was prepared under the same conditions as in Example 2, except that the 3-phenyl-1,1-dimethylurea catalyst was further included.

Example 6

A structural adhesive was prepared under the same conditions as in Example 4, except that it further contained 1 part by weight of tetrabutylphosphonium tetrafluoroborate.

[Table 1]

[Table 2]

2. Method for evaluating physical properties and results

The following items were evaluated using the structural adhesives prepared in Examples 1 to 6 and Comparative Examples 1 to 5, and the measurement results are shown in the following [Table 3].

(1) Flexural strength (N / mm ² ): Measured according to KSM 3015.

(2) Tensile strength (N / mm ² ): Measured according to ASTM D790.

(3) Mutual layer adhesion (kgf / 25mm): measured according to asida-DZC-5.

(4) Flame retardance: measured according to the UL-94 method.

[Table 3]

Referring to Tables 1 to 3, Examples 1 to 5 satisfying the structural adhesive composition of the present invention showed high overall results in flexural strength, tensile strength, adhesive strength, and flame retardancy.

In particular, Example 6 further comprises 1 part by weight of tetrabutylphosphonium tetrafluoroborate. By including, it shows a result of higher flexural strength and tensile strength compared to Examples 1 to 5.

However, in Comparative Examples 1 to 5, the result was low, or physical properties were not measured.

Therefore, the structural adhesive according to the present invention can exhibit a flexural strength of 35 to 50 N / mm ² , a tensile strength of 60 to 70 N / mm ² , an adhesive strength of 25 to 35 kgf / 25 mm, and excellent flame retardancy by including surface treated silica particles and HNT. have.

The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and may be manufactured in various different forms, and having ordinary knowledge in the art It will be understood that a person can be implemented in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (5)

With respect to 100 parts by weight of the bisphenol-based epoxy resin, 1 to 20 parts by weight of a reactive diluent containing an epoxy group, 20 to 40 parts by weight of an acid anhydride-based compound, 1 to 15 parts by weight of a curing accelerator containing an imidazole derivative, first silane 10-20 parts by weight of the silica particles surface-treated, 1-20 parts by weight of Halloysite NanoTube (HNT) surface-treated with a second silane, and 0.1-2 parts by weight of an additive containing a silicone antifoaming agent and a silicone leveling agent Including wealth,
Structural adhesive, characterized in that it further comprises 0.1 to 1 part by weight of a catalyst comprising an aliphatic urea compound.
According to claim 1,
The acid anhydride-based compound is a structural adhesive, characterized in that it comprises at least one of HHPA (Hexahydro phthalic anhydride), MeHHPA (Methyl hexahydro phthalic anhydride), THPA (Tetra hydro phthalic anhydride) and MeTHPA (Methyl tetrahydro phthalic anhydride).
According to claim 1,
Structural adhesive characterized in that the silica particles surface-treated with the first silane have a diameter of 1 to 20 μm.
According to claim 1,
Each of the first silane and the second silane is 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldime Structural adhesive comprising at least one of methoxysilane and 3-chloropropyltrimethoxysilane.


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