JPH058088B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a melt coating method for melt-coating a solid resin that is solid at room temperature and has heat-fusibility or thermoplasticity to a base material, and is used to form a protective film. Melt coating of resinous substances such as agents, adhesives, adhesives, etc. to base materials,
It is a new coating method that can be widely applied especially to plate-like or sheet-like substrates of uniform thickness, and can be widely used in fields requiring surface coating, lamination, etc.

[Conventional technology]

BACKGROUND ART Conventionally, it has been widely practiced to apply a resin that has been brought into a molten state or a fluidized (plasticized) state by heat onto a substrate using a heated roll.

Particularly in the field of hot melt adhesives, devices that combine an adhesive melting tank with a wheel or a transfer roll have become widely used and are widely used in applications such as adhesion and lamination.

In addition, equipment such as fountain coaters and coating guns that combine slit nozzles and melting tanks,
Coating using an extruder is also conventionally known.

Among these methods, the method using a hot roll is the simplest method that allows direct transfer of a molten or fluid material onto a substrate, and is capable of coating a large area at low cost.

On the other hand, as shown in Japanese Patent Application Laid-open No. 59-177159, a hot melt adhesive in the form of powder is supplied to a partitioned adhesive pool between a pair of heating rolls and a weir plate, and this is applied by the heating rolls. A melt coating method has also been proposed in which the sheet is melted by heating and formed into a sheet between the rolls and transferred onto the surface of the material to be coated.

[Problem that the invention seeks to solve]

In the known method, the method using a melting tank inevitably requires a long residence time, so it is difficult to avoid deterioration and coloring of the resin component due to long-term heating.
In particular, there have been problems with the application of resins that have properties such as thermal decomposition and thermosetting properties and have poor heat stability.

In addition, the method using an extruder, which has the characteristic of melting or fluidizing powder or granular material in a short time, requires a large area of equipment and is expensive, so it cannot be applied in all cases. .

Furthermore, in the melt coating method disclosed in JP-A-59-177159, since the coating transfer roll also serves to melt the resin, unmelted solid resin tends to remain on the transfer roll, resulting in stable coating. It has a number of drawbacks, including the inability to form a film, the inability to obtain a stable film thickness due to uneven resin temperature, and the difficulty of continuous coating because the melting operation takes time. .

[Means for solving problems]

In view of the current situation, this invention is the result of numerous studies on a melt coating method using a heated roll method that does not use a melting tank method, with the aim of providing a method that enables inexpensive, simple, and stable coating. When melting or fluidizing and applying the obtained solid resin, which is solid at room temperature and has heat-melting properties or thermoplasticity, onto a substrate, the following steps (a) to (c) are carried out in sequence. This melt coating method is characterized by:

(a) A step in which the solid resin is supplied to a melting tank having a heating grid inside thereof, and the solid resin is melted or fluidized by the heating grid to form a liquid resin.

(b) A step of supplying the liquid resin melted or fluidized in the melting tank between a pair of coating heat rolls whose temperature can be adjusted.

(c) The liquid resin supplied in step (b) is spread in a sheet form between the pair of coating heat rolls, and a base material is conveyed in close proximity to one of the coating heat rolls. The process of applying it to the surface of.

In the method of this invention, a solid resin that is solid at room temperature and has heat-melting or thermoplastic properties refers to a resin that is generally solid at room temperature (approximately 25°C) and becomes molten or fluid at a predetermined heating temperature. The form of the resin before being supplied to the melting tank may be in the form of powder or granules, or may be in the form of blocks.

In the above step (a), the solid resin that is solid at room temperature and has heat-fusibility or thermoplasticity is supplied to the melting tank, but this melting tank is not just a conventional tank-type melting tank, but has a solid resin inside. This is a melting tank with a heating grid for melting or fluidizing the resin.

This melting tank has an inlet for the solid resin at the top and a slit-shaped outlet for the melted or fluidized liquid resin to flow down at the bottom, and has a heating grid inside to melt or fluidize the solid resin. (Hereinafter, the resin in such a state will be referred to as a liquid resin) and has a structure that allows it to be uniformly supplied between coating hot rolls located under, preferably directly below, the melting tank.

A heating grid is a grid-shaped heating element that is placed in the melting tank and uses electricity or other heat sources to heat the solid resin inside to a predetermined temperature to melt or fluidize it. The roughness is selected depending on the particle size of the solid resin to be supplied, the viscosity of the liquid resin, etc.

Note that by providing the heating grid as low as possible in the lower part of the melting tank, the residence time of the resin can be shortened.

The hot rolls for coating in steps (b) and (c) are placed under the melting tank, and consist of a set of two hot rolls, one of which is a coating roll and the other is a doctor roll, etc. By finely adjusting the spacing between these rolls, the film thickness of the sheet-like liquid resin applied to the substrate can be set to a predetermined thickness.

In addition, by providing a weir plate at both right and left end portions of the pair of coating hot rolls, spanning between both rolls, and making the area between the weir plates a retention area for the liquid resin, the above-mentioned pair of coating The liquid resin can be uniformly supplied from the hot roll.

Furthermore, a liquid level sensor for detecting the liquid level of the liquid resin is provided in the liquid retaining part, and this liquid level sensor is electrically linked with the heating grid, so that the liquid resin in the liquid retaining part is If the liquid level falls, the amount of heat generated by the heating grid will be increased to increase the melting or fluidization of the solid resin in the melting tank, increasing the amount of liquid resin supplied to the lower liquid retention area, and increasing the When the liquid resin is stored in the reservoir and a predetermined liquid level is reached, the amount of heat generated by the heating grid is reduced, and the supply of liquid resin to the liquid retention area is reduced, thereby reducing the liquid level of the liquid resin in the liquid pool. It can be kept in any position at all times.

The liquid resin formed into a sheet by the hot coating roll is applied onto a substrate that is conveyed close to one of the coating rolls in step (c).

The material of the set of two coating heat rolls may be any heat-resistant material, but in order to transfer the liquid resin film,
As for the surface material, the coating roll is preferably made of heat-resistant resin, rubber, etc., and the doctor roll is preferably made of metal, ceramics, heat-resistant resin, rubber, etc.; Preferably, they are different from each other.

[Effect]

Specifically, in the method of the present invention, a solid resin A is charged into a melting tank 2 installed at the top of a coating device 1 as shown in the attached drawings, and a heating grid 3 of the melting tank 2 is charged.
The thus obtained liquid resin B is transferred from the lower part of the melting tank 2 to a pair of coating hot rolls 4 and 5, one of which is a coating roll and the other a doctor roll, and weir plates 8a and 8b. The liquid is caused to flow down into the liquid retention area 10 formed between the two.

Next, the liquid resin B is transferred between a set of two coating hot rolls 4 and 5 to form a sheet-like resin C, and the sheet-like resin C is applied onto the base material 9. The temperature of the liquid resin B can be maintained at a predetermined temperature by equipping both the hot coating roll 4 serving as a coating roll and the hot coating roll 5 serving as a doctor roll with heating means that can adjust the temperature. It can be easily applied.

The liquid resin B supplied to the pair of heating rolls 4 and 5 for coating is continuously supplied in a melted or fluidized state by the melting tank 2 in the preceding stage, so that there is no unused material. The solid resin A in a molten or non-flowing state does not remain on the coating hot rolls 4 and 5, and can be continuously and stably applied to the substrate 9.

Note that although the coating heat rolls 4 and 5 are normally rotated in different directions, they can also be rotated in the same direction under specific conditions such as when the supply amount and viscosity of the liquid resin B are low.

Coating to the base material 9 is carried out by supporting the base material 9 with a support roll 6 provided in close proximity to the coating roll 4, and applying the liquid resin B onto the sheet resin C. Coating can be easily carried out by conveying it in contact with the coating roll 4.

〔Example〕

Hereinafter, an example of an apparatus for implementing the method of the present invention will be specifically described with reference to the drawings.

As shown in FIGS. 1 and 2, a coating apparatus 1 which is an example for carrying out the method of the present invention is equipped with a melting tank 2 having a heating grid 3 therein, and a heating means whose temperature can be adjusted. It is composed of a pair of hot coating rolls 4 and 5, and a support roll 6 provided in parallel below and adjacent to one of the hot coating rolls 4.

The melting tank 2 forming a part of the coating device 1 includes:
an input port 2a for inputting solid resin in the upper part;
It is a horizontally elongated box body with a slit-shaped outlet 2b at the bottom through which melted or fluidized liquid resin flows down, and the lower part of each longitudinal side is bent inward to form the above-mentioned shape at the bottom. A slit-shaped outlet 2b is formed, and a heating grid 3 is attached to the lower part of the inside thereof, and the heating grid 3 heats the solid resin introduced from the inlet 2a and melts or fluidizes the resin. The resin is configured to be uniformly supplied from the outlet 2b between coating hot rolls 4 and 5 located directly below the melting tank 2.

The heating grid 3 is a grid-shaped heating element, and the melting tank 2
The heating grid 3 is placed at the bottom of the interior and is heated to a predetermined temperature using electricity or other heat sources to melt or fluidize the solid resin inside. It is determined by the particle size and viscosity of the liquid resin.

The two coating heat rolls 4 and 5 have one of them as a coating roll 4 and the other as a doctor roll 5, and both are composed of rolls with smooth surfaces, and one of them is a coating roll 4, and the other is a doctor roll 5. The coating heat roll 4 is constructed of a roll having a larger diameter than the other coating heat roll 5, and each of the coating heat rolls 4 and 5 is provided with heating means capable of controlling the temperature inside.

Examples of the heating medium in the temperature-adjustable heating means include steam, water, hot water, or circulating oil, but an electric or electromagnetic heater may be used instead.

Furthermore, weir plates 8a and 8b are respectively provided between the coating heat rolls 4 and 5 near both left and right ends thereof, and a liquid retention area 10 is formed between the pair of coating heat rolls 4 and 5. The liquid resin B flowing down from the melting tank 2 is evenly distributed and supplied between the coating heat rolls 4 and 5, and the liquid level of the liquid resin B staying in the liquid retention part 10 is detected. A liquid level sensor 7 is provided, and this liquid level sensor 7 is interlocked with the heating grid 3 of the melting tank 2, and the liquid level sensor 7
When the liquid level of the liquid resin B at 0 falls, the temperature of the heating grid 3 is raised to increase the melting or fluidization of the solid resin A in the melting tank 2, and the liquid resin B is supplied to the liquid pool directly below.
When the supply amount is increased and the liquid resin melted in the liquid retention section 10 exceeds a predetermined liquid level, the temperature is lowered to keep the liquid level constant at all times.

The melt coating device 1 having such a configuration melts or fluidizes the solid resin A supplied to the melting tank 2 using the heating grid 3 of the melting tank 2 to form a liquid resin B, which is then transferred to the melting tank 2. By uniformly flowing down onto the coating heat rolls 4 and 5 from the bottom and rotating the coating heat rolls 4 and 5 in different directions in the direction of the arrow, the sheet-shaped resin C suitable for coating is formed. Shape.

The obtained sheet-like resin C is applied to the surface of a base material 9 that is conveyed by a support roll 6 that is disposed in parallel and close to the lower side of one of the coating heat rolls 4. is applied continuously.

〔Effect of the invention〕

The melt coating method of the present invention, which consists of the steps (a) to (c) described above, can successfully and easily perform melt coating on base materials of various synthetic resins that have conventionally had problems with thermal stability. It has many advantages as described below.

Melting and melting of thermomeltable or thermofluid resins
The liquid feeding process time is short, so deterioration due to heat is less likely to occur.

During work, the residence time of the heat-melting or heat-flowable resin is short, so the heat-melting is performed evenly, so that the resin etc. are not easily denatured by heat even during long-time work.

Because the resin is directly and continuously supplied to the hot roll part for coating in a completely molten or fluid state,
Beautiful and stable coating can be performed continuously.

Since the apparatus for carrying out the method of the present invention is handled in an openable zone, the apparatus can be easily cleaned after work, and there is no need to replace parts due to blockage of powder or granules.

Furthermore, since the melt coating method of the present invention has the above-mentioned advantages, it also has features such as being applicable to the uses described below.

Melt coating or lamination of resins whose viscosity decreases significantly due to thermal decomposition.

Melt coating or lamination of resins that are highly colored due to thermal denaturation.

Melt coating or lamination of reactive hot melt adhesives or adhesives.

Coating of reactive heat-melt adhesives, etc. to porous substrates such as honeycomb cores during the manufacture of honeycomb core sandwich structures.

[Brief explanation of the drawing]

FIG. 1 is a simplified perspective view showing an example of a coating apparatus for carrying out the method of the present invention, and FIG. 2 is a sectional view taken along the - line in FIG. 1. 1... Coating device, 2... Melting tank, 3... Heating grid, 4... Heat roll for coating, 5... Heat roll for coating, 6... Support roll, 7... Liquid level sensor , 8a, 8b... weir plate, 9... base material, 10...
Liquid retention part, A...solid resin, B...liquid resin, C...
...Sheet resin.

Claims (1)

[Scope of Claims] 1. When melting or fluidizing and coating a solid resin that is solid at room temperature and has heat-melting or thermoplasticity onto a base material, each of the following steps (a) to (c) is sequentially performed. A melt coating method that is characterized by: (a) A step in which the solid resin is supplied to a melting tank having a heating grid inside thereof, and the solid resin is melted or fluidized by the heating grid to form a liquid resin. (b) A step of supplying the liquid resin melted or fluidized in the melting tank between a pair of coating heat rolls whose temperature can be adjusted. (c) The liquid resin supplied in step (b) is spread in a sheet form between the pair of coating heat rolls, and a base material is conveyed in close proximity to one of the coating heat rolls. The process of applying it to the surface of.