JPH0238042A - Production of surface coated steel plate for thermal adhesion - Google Patents

Abstract

PURPOSE:To enhance blocking resistance and weldability by adding an emulsion of a thermosetting epoxy resin to an emulsion of a specific thermoplastic acrylic resin and further adding a predetermined amount of a high temp. reaction type curing agent to prepare a liquid mixture and applying said mixture to the surface of a steel plate to bake the coating layer. CONSTITUTION:On a resin wt. basis, 5-120pts.wt. of an emulsion of a thermosetting epoxy resin having a glass transition point of 55-150 deg.C is added to 100pts.wt. of an emulsion of a thermoplastic acrylic resin having a glass transition point of 55-150 deg.C and a high temp. reaction type curing agent is further added thereto within a range of + or -20% of the stoichiometric addition amount of the epoxy resin to prepare a liquid mixture which is, in turn, uniformly applied to the surface of a steel plate and baked. The thickness of the dry film after the coating and baking of the liquid mixture is desirably 0.5-10mum.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a method for manufacturing a surface-treated steel sheet that is used by bonding by pressurizing and heating after punching, shearing, or press working, and particularly relates to a method for manufacturing a surface-treated steel sheet that is used by bonding by pressing and heating after punching, shearing, or pressing. It can be advantageously used for forming an insulating film.

<Prior art> Properties required for the surface coating of surface-treated steel sheets that are bonded by pressure and heat are pressure/heat adhesion, bronking resistance, weldability, punchability, shearability, and press workability. There are many examples, such as durability and corrosion resistance.

Many studies have been conducted to meet these demands, and many proposals have been made regarding surface treatment methods and surface treatment film compositions.

As an example of using a mixture of an acrylic resin emulsion and an epoxy resin emulsion, a rust-proof steel plate for automobiles is known in Tetsu to Hagane J No. 72, No. 8, P 1038-1043 (1986). This study investigated the mixing ratio of acrylic composite silicate, which is characterized by corrosion resistance, and epoxy composite silicate, which is characterized by paint adhesion, and the silica sol component ratio, in order to obtain overall excellent quality characteristics as an organic composite silicate. The purpose and use of the present invention are completely different.

Furthermore, the water-soluble coating composition using acrylic and epoxy disclosed in Japanese Patent Publication No. 13456/1983 is a water-soluble epoxy-modified alkyd resin in which one or more acrylic functional monomers are added to the water-soluble epoxy-modified alkyd resin. 1 to 30 parts by weight per 100 parts by weight of epoxy-modified alkyd resin
A water-soluble coating composition comprising a resin obtained by adding parts by weight and heating and addition polymerizing, for 100 parts by weight of the above resin,
It is characterized in that 0.1 to 1.0 parts by weight of a titanate coupling agent is uniformly dispersed. However, this invention is a tin-lead alloy plating material used as a material for vehicle fuel tanks, etc., that is, parts where rust prevention is particularly required.
This invention relates to a temporarily provided water-soluble paint composition, and its purpose and application are completely different from those of the present invention.

As a surface-coated steel plate for heat bonding, Japanese Patent Publication No. 528998
The following is disclosed in the publication:

When applying a treatment liquid containing thermoplastic resin and thermosetting resin as main components to the surface of a steel plate, mix 0.1 to 1.2 parts of thermosetting resin to 1 part of thermoplastic resin. The treated solution is made into a water emulsion by adding 0.1 to 0.8 parts of an emulsifier to 1 part of the resin component and further adding water. This is a method for producing a surface-coated steel plate for adhesive use, which comprises uniformly applying and drying the adhesive on the surface of the steel plate.

In addition, Japanese Patent Publication No. 52-8999 discloses that an acrylic resin water emulsion and a water-soluble phenol resin are applied to the surface of a steel plate.
A method for manufacturing a surface-coated steel sheet for adhesive use is disclosed, which comprises uniformly applying and drying a mixture with a water-soluble melamine resin, and baking the coating film in an incomplete state.

<Problems to be Solved by the Invention> However, although steel sheets with a surface coating obtained by the above-mentioned method have good adhesive properties under pressure and heat, they may cause problems such as blocking depending on the storage conditions before use at the customer's site. It was happening.

It is also possible to use such a surface coating as an insulating coating.
IF W44 is used as the iron core of transformers, motors, etc. After slitting, an electric & f steel sheet coil having an insulating film with good pressure and heat adhesion is punched into a core, which is then laminated to form a core block by pressure and heat adhesion, and assembled into the required parts. In the case of a small power transformer, the wires are wound after forming an E core block and an I core block, and the E core block and I core block are joined by welding, but there is a drawback that this cannot be done.

Therefore, an object of the present invention is to propose a method for manufacturing a surface-coated steel plate for heat bonding that has excellent anti-blocking properties and weldability.

<Means for Solving the Problems> The present invention was developed as a result of extensive research to advantageously solve the above-mentioned problems. For 100 parts by weight of the resin content in the emulsion of thermoplastic acrylic resin at 150°C, 5 to 120 parts by weight of the resin content in the emulsion of thermosetting epoxy resin with a glass transition point (Tg) of 55 to tso'c. In addition, a mixture solution containing a high-temperature-reactive curing agent in a range of ±20% of the chemical addition amount of the epoxy resin is uniformly applied and baked. This is a method for manufacturing a surface-coated steel plate for heat bonding with excellent weldability.

Function> As the base steel plate used in the present invention, both hot-rolled plates and cold-rolled plates of mild steel plates, electromagnetic steel plates, stainless steel plates, and special steel plates can be used, and m is not particularly limited. do not have. In addition, Zn, Ni,
Metal plating such as Sn or Cr, Zn-Ni, Zn
Metal alloy plating such as -Fe or Zn-(:u) may be applied, and further chemical conversion treatment such as chromate or bonding may be applied directly to the surface of the steel sheet or to the surface of the plating. There is no particular limitation on the presence or absence of a coating on the surface of the steel plate, such as zero or more in which an insulating coating may be applied to the surface.

The present inventors conducted a research investigation to elucidate the cause of blocking, and found that it is related to the Tg (glass transition point) of the fracture surface coating.

It was also found that the quality of weldability is related to the thermal decomposition of the resin as a coating component, and that this is related to Tg.

That is, a coating made of a resin with a low Tg tends to block during storage, and is also susceptible to thermal decomposition during welding, and therefore generates a large amount of gas due to thermal decomposition. Therefore, even when the molten metal of the weld bead during welding solidifies, gas continues to be generated, resulting in the formation of blowholes. Therefore, the strength of the welded part decreases, resulting in poor welding. On the other hand, resins with a high T point are difficult to bronking, generate less pyrolysis gas during welding, do not leave blowholes in the weld bead, and exhibit good weldability.

The glass transition point of the thermoplastic acrylic resin used in the present invention (
Tg) is limited to the range 55-150'C.

When TP is less than 55°C, blocking is too strong and the steel sheet cannot be used as a surface-coated steel sheet. Another disadvantage is that weldability deteriorates. On the other hand, if the Tg exceeds 150'C, the coating obtained by coating and baking will be too hard and will not exhibit sufficient adhesion performance during pressurization and heating.

(Meth)acrylic acid is used as a non-functional monomer constituting the thermoplastic acrylic resin used in the present invention.

The (meth)acrylic acid ester group includes 01 to C8 compounds, and the alkyl groups of these esters include methyl, ethyl, propyl, butyl, isodecyl, lauryl, dodecyl, cetylstearyl, ethylhexyl, and cyclohexyl. group, octyl group, benzyl group, etc. can be used.

- as a functional monomer, having a functional group such as the carboxyl group or hydroxyl group of (meth)acrylic acid, such as methacrylic acid, dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, tert-butylaminoethyl methacrylate. , 2-hydroxypropyl methacrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, tetrahydrofurfuryl methacrylate, etc. can be used. In addition, polyfunctional monomers such as diethylene glycol dimethacrylate may also be used.

Other monomers that can be copolymerized with at least one of these heptamers are not particularly limited, and alkyds, phenol, α-olefins such as ethylene and propylene, styrene, and the like can be used.

7855 to 100 parts of resin in thermoplastic acrylic emulsion at 7855 to 150°C of ff+fJ
The resin content in the 150°C thermosetting epoxy emulsion is limited to 5 to 120 fflfft parts. If it is less than 5 parts by weight, weldability deteriorates, and if it exceeds 120 parts by weight, the epoxy resin is expensive and economical efficiency decreases.

If the Tg of the thermosetting epoxy resin is less than 55°C, blocking resistance and weldability will decrease. On the other hand, Tg is 150'
If it exceeds C, the coating will be too hard and will not be able to exhibit sufficient adhesion performance during pressurization and heating. Therefore, thermosetting epoxy resin 18 is limited to 55-150'C.

Monomers constituting the thermosetting epoxy resin used in the present invention include bisphenol Δ bisphenol F, bisphenol S resorcinol he-1'-4+ hydrobisphenol A dicrycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglysodylether, phthal Acid diglycidyl ester, dimer acid diglycidyl ester, 1-liglycidyl isocyanate I, tetraglycidyldiaminodiphenylmethane, tetraglycidylmethaxomendiamine.

Cresol novolane polyglycidyl ether etc. can be used.

The curing agent used for these is not limited to any material that causes a curing reaction during coating and baking, and high-temperature reactive curing agents include aromatic polyamines, acid anhydrides, and phenolic resins (novolac type and rezul type). , amino(d-fat), dianediamide, and hydrazide compounds.

Further, the above-mentioned acrylic resin is not used as a curing agent for epoxy resin.

The appropriate amount of the curing agent to be added can be calculated as the stoichiometric amount from the ratio of the epoxy equivalent and active hydrogen equivalent of the epoxy resin. An increase or decrease within a range of ±20% with respect to this appropriate amount is allowed. It has been confirmed that the reaction temperature between the epoxy resin and the curing agent is sufficient to exhibit its performance at the normal baking temperature after coating, and the temperature range is not particularly limited.

Therefore, the maximum Tg can be reached with the above-mentioned appropriate addition amount of the curing agent, and TH decreases only slightly within the range of +20%.

The method for applying the liquid mixture is not particularly limited and may be any known coating method such as a roll coater, curtain flow coater, spray coating, or squeeze coater.

As a method for baking the mixed liquid, a hot air drying furnace, an induction heating furnace,
A known baking furnace such as a resistance heating furnace can be used without any particular limitation.

The dry film thickness after coating and baking the mixture is preferably 0.5 to 10 μm.

If the film thickness is less than 0.5 μm, the desired adhesive force cannot be obtained unless the pressure applied during heating and pressing is significantly increased, which is not economical. Further, if the film thickness is 10 μm or more, a dramatic improvement in adhesive strength cannot be expected, and this is because it is not economical and tends to cause blocking.

The final baking plate temperature is preferably 150 to 450''C.

If it is below 150°C, it will be insufficiently sintered, easily blocking, and corrosion resistance will also decrease. At 450° C. or higher, a situation occurs in which good adhesive strength cannot be obtained and corrosion resistance also decreases.

<Example> Examples of the present invention will be described below along with comparative examples.

Example 1 100 parts by weight of an acrylic resin emulsion resin having a coating Tg of 114° C. was synthesized as follows.

Water, Emal 10 (registered trademark of Kao ■) anion activator, and potassium persulfate were added to ethyl methacrylate monomer, ethyl methacrylate monomer, and acrylamide monomer, and the mixture was heated and maintained at 70°C in a flask for 6 hours. A stable resin emulsion with a yield of 99.5% was subsequently obtained.

Resin 80!INI portion of the 119 T g 97 ''C epoxy resin emulsion was synthesized as follows.

Bisphenol A-Epichlorohydrin mJIL Polyethylene glycol ether of sorbitan palmitate,
Water was added to a 5% polyvinyl alcohol aqueous solution, and the above mixture was mixed in a flask to form an emulsion.

To these, 13 parts by weight of an ammonium salt of a diaminosophenyl sulfone compound was added as a curing agent. This is an increase/decrease of +18% from the stoichiometric amount of epoxy resin added.

The mixture thus obtained was coated with 0.5 mm thick Si 0.1
%.

8l 0.05%, MnO, 1%, CQ, 01
It was coated on a silicon steel plate containing 5% with a roll coater, and then baked in an electric furnace at a final plate temperature of 290°C to obtain a film thickness of 5 μm.

Comparative Example 1 As a comparative example, ethyl methacrylate was synthesized in the same manner as in the synthesis of the acrylic resin emulsion in Example 1.

Using ethyl acrylate, coat 1! An acrylic acid resin emulsilon having a temperature of JTg -2°C was synthesized, and using the same material as in Example 1, it was coated and baked in the same manner as in Example 1 to obtain a film having a thickness of 4.9μ.

Measurement of shear tensile strength was carried out after punching these samples, stacking them in a single wrap, heating the sample to 200° C. while applying a pressure of 10 kg/c+Il, and allowing it to cool.

As a result, in the example, a good result was obtained with a shear tensile strength of 156 kg/cd. On the other hand, that of the comparative example is 123 kg/c
It was f. Furthermore, the fact that the shear tensile strength is large means that M,
When used in magnetic steel sheets, it is highly effective in reducing noise caused by magnetostriction.

To measure the blocking resistance, the samples were laminated with a single wrap in the same way as above, and the sample was heated at 80℃2 with a pressure of 200kg/c4.
After aging for one day, it was left to cool.

In the example, the blocking strength was 7.6 kg/cm, which is a level that does not pose any practical problem, but in the comparative example, it was 120 kg/cm.
/ ct, which was a bad level.

Weldability was determined by stacking the samples after punching to a thickness of 30 nm + TI
A G welding test was conducted. In the example, the welding speed was 100
cm/mm, but the comparative example showed good weldability up to 2 cm/mm.
Even 0cm/m? A blowhole occurred in the standing bead, resulting in poor weldability.

Other coating properties were as shown in Table 1.

Table ■ (1) Interlayer resistance JIS method 2 (2) Adhesion judgment Judging by peeling off the bending tape in the middle of the 10 fins: No peeling at all: O1 Partial peeling: Δ.

Complete peeling: × (3) Corrosion resistance 5ST 72 hours rust area (%)
Also, other Examples 2 to 6. The results of Comparative Examples 2 to 4 are shown in Table 2. In each case, various resin emulsions were synthesized in accordance with Example 1.

<Effects of the Invention> As described above, according to the present invention, it has become possible to produce a surface-coated steel sheet for heat bonding that has excellent heat bonding properties and also has good blocking resistance and weldability, which were difficult to do in the past.

Claims (1)

[Claims] A resin content of 100% in an emulsion of thermoplastic acrylic resin with a glass transition point (Tg) of 55 to 150°C was applied to the surface of the steel plate.
Glass transition point (Tg) is 55 to 150 based on weight part
Resin content in emulsion of thermosetting epoxy resin at ℃5
~120 parts by weight of the epoxy resin is added, and a high-temperature-reactive curing agent is added thereto in a range of ±20% of the stoichiometric amount of the epoxy resin, and a mixed solution is uniformly applied and baked. A method for producing a surface-coated steel plate for heat bonding with excellent blocking resistance and weldability.