WO2020197485A1

WO2020197485A1 - Composition comprising fluororesin and methods of producing the composition and a fluororesin dispersion

Info

Publication number: WO2020197485A1
Application number: PCT/SG2019/050158
Authority: WO
Inventors: Eason CHAN; Siew Peng CHIA; Sho Masuda
Original assignee: Agc Asia Pacific Pte. Ltd.
Priority date: 2019-03-22
Filing date: 2019-03-22
Publication date: 2020-10-01
Also published as: CN113455109A; TW202100619A

Abstract

A composition, a method of producing the composition and a method of producing a fluororesin dispersion from the composition, wherein the composition comprises: (i) a fluororesin having an average particle diameter of 1 μm or more and 5 μm or less and a maximum particle size of 10 μm or less; (ii) a dispersant; and (iii) an organic solvent, wherein percentage by mass of the organic solvent in the composition is 0.2% or less.

Description

COMPOSITION COMPRISING FLUORORESIN AND METHODS OF PRODUCING THE COMPOSITION AND A FLUORORESIN DISPERSION FIELD OF INVENTION The present invention relates to a composition comprising fluororesin, and methods of producing the composition and a fluororesin dispersion.

BACKGROUND Fluororesins are used as coatings because they have the characteristics of being chemical resistant, heat resistant, having a low coefficient of friction, and being electrically insulating. Specifically, fluororesins are used as coatings in high frequency circuit boards due to their excellent dielectric characteristics. In a typical process of manufacturing high frequency circuit boards, the fluororesin is processed into fine particles, dispersed in a dispersion medium containing a matrix resin, and then laminated together with a conductor such as a copper foil and the like. The resulting panel is then further processed by etching or the like to form the high frequency circuit board. As the matrix resin normally used in the above mentioned manufacturing process is soluble in a hydrocarbon solvent, it is necessary to first disperse the fluororesin in the hydrocarbon solvent. However, due to its low interfacial tension, the fluororesin has poor wettability with the hydrocarbon type medium and is difficult to disperse in the said medium. Furthermore, considering the relatively high specific gravity of fluororesin, it is practically difficult to avoid separation in the fluororesin dispersion. Conventionally, it is necessary to respond industrially such as maintaining the dispersion state by continuous stirring and setting a pot life after dispersion. This separation problem is especially evident during transportation. Another issue that may arise during transportation of fluororesin dispersion is that organic solvents are generally hazardous to handle, which not only increases the transportation cost but also increases the transportation period. Various methods have been proposed for the dispersion technique of fluororesin. JP-A-2017-193655 discloses a fluororesin dispersion containing a dispersant having a thermally decomposable group with a specific oxyaikyiene chain, fluororesin particles and water or an organic solvent.

JP-A-1987-121700 discloses a fluororesin dispersion characterized by dispersing a fluorine- containing resin powder having a particle size of 2 mm or less in an organic solvent.

Japanese Patent 2516241 discloses a technique of dispersing a fluorine-containing resin powder having a particle diameter of 2 mm or less in an aqueous medium in the presence of a non-ionic surfactant and a thickener.

Japanese Patent 4255169 discloses a dispersant having an organosiloxane structure which uniformly disperses fibrillated PTFE.

Japanese Patent 5195425 discloses a technique of bringing a solution in which a fluororesin is roughly dispersed in an aqueous medium to an ion exchange resin, adding an electrolyte and an anionic emulsifier, and then subjecting to phase separation and concentration to obtain an aqueous fluororesin solution.

JP-A-1998-176002 discloses a technique in which polymer particles insoluble In an organic solvent are dispersed by a polymer having an acrylic skeleton and having a fluoroalkyl group in a side chain.

US 2013/0149540 discloses a charging roll composition for improving the copy quality of a dry copying machine, and a technique of dispersing polytetrafluoroethylene resin particles with a polymer having an acrylic skeleton and a fiuoroaikyi group in a side chain has been disclosed in the examples.

WO 2018070420 discloses a composition obtained by mixing a water-containing fiuoropolymer having a specific sulfonic acid group and a carboxyl group on its structure with water and mesh filtering with a mesh opening size of 20 mm to obtain a composition having a degree of dispersion of 50%. Drying at a work amount of 200 W or less to obtain a powder is disclosed.

As mentioned above, Japanese Patent 2516241 and Japanese Patent 5195425 disclose the use of water as a dispersion medium. However, the use of water as a dispersion medium increases the time taken for the application of the fluororesin coating onto the substrate due to the large latent heat of evaporation of water. Furthermore, the presence of a dispersing agent and a thickener for stabilization of the aqueous dispersion could result in the loss of dielectric properties of fluororesin. JP-A-1998-176002 and US 2013/0149540 disclose a technique for producing a non- aqueous dispersion by using a polymer having an acrylic skeleton and having a fluoroalkyl group in a side chain. However, with the presence of the non-fluorine portion in the polymer, there is a possibility that the properties possessed by the fluororesin may be hindered in high frequency integrated circuit applications. WO 2018070420 discloses an ion exchange resin having a sulfonic acid group or a carboxyl group which has a high affinity for water as a dispersion solvent itself but cannot be used for a high frequency circuit board where electrical insulation is required. It also suggests the possibility of dispersing the ion exchange resin in organic solvents other than water, but the examples are not shown. SUMMARY OF THE INVENTION According to an example of the present disclosure, there are provided a composition comprising fluororesin, a method of producing the composition, and a method of producing a fluororesin dispersion as claimed in the independent claims. Some optional features are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A illustrates steps for forming a composition according to an example of the present disclosure. Figure 1B illustrates steps for producing a fluororesin dispersion from the fluororesin composition of Figure 1A. DETAILED DESCRIPTION Examples of a composition and a method of producing the composition and a fluororesin dispersion from the composition are described as follow. Figure 1A illustrates steps for forming an example of a composition 104 of the present disclosure. The composition 104 in this case is a fluororesin composition. This fluororesin composition 104 is a dry solid in the present example. The following components are first mixed together in a step 1: (a) a fluororesin powder, (b) a dispersant, (c) a solvent and (d) dispersing beads resulting in a mixture 101. It is also possible to use other suitable dispersing aids besides dispersing beads. In a step 2, which is regarded as a dispersion step, the fluororesin powder in the mixture 101 is dispersed by mechanical action. Dispersion by mechanical action may include shaking the mixture using a paint shaker. Subsequently, in a step 3, the dispersing beads are removed by filtration using a suitable filter 102 (see examples of such filter in the Examples described under the EXAMPLES section below) to form a first fluororesin dispersion 106. Finally, in a step 4, the first fluororesin dispersion 106 is dried to form the dry-solid fluororesin composition 104 of the present example. The drying process of step 4 may be a constant drying process with check-points during the process to confirm that the percentage by mass of the organic solvent in the composition 104 is 0.2% or less. In another example, the drying process can be such that the first fluororesin dispersion 106 is subject to drying more than once at the same temperature or with fluctuating temperatures with stops or check-points in-between to confirm that the percentage by mass of the organic solvent in the composition 104 is 0.2% or less. The percentage of 0.2% or less of the solvent ensures that the composition 104 is sufficiently dry. The confirmation step at each stop or check-point to ensure that the percentage by mass of the solvent in the composition 104 is 0.2% or less may be in the form of subjecting the composition 104 to a heating process, and determining the mass of the composition 104 before and after the heating process to verify that the percentage change in the mass of the composition 104 is 0.2% or less. After the drying process, the finding that the percentage change in the mass of the composition 104 is 0.2% or less can conclude that the percentage by mass of the solvent in the composition 104 is 0.2% or less. In the example of forming a composition 104 as illustrated in Figure 1A, the components are added in the following parts per mass in step 1:

1 to 40 parts per mass of the fluororesin;

1 to 10 parts per mass of the dispersant; and

50 to 98 parts per mass of the first organic solvent,

such that the total parts per mass of the said components add up to 100.

The dispersing beads is then added in 10 to 20 parts per mass per 100 parts of the mixture of fluororesin, dispersant and first organic solvent. Figure 1 B illustrates steps for producing a second fluororesin dispersion from the dry-solid fluoresin composition 104 produced in the example of Figure 1 A. in a step A, a second solvent 204 is first added to the dry-solid fluororesin composition 104 of Figure 1 A to form a mixture 201. In a step B, the mixture 201 is subjected to a redispersion step to redisperse the fluororesin in the mixture 201 by mechanical action to form the second fluororesin dispersion 202.

In the example of producing the second dispersion 202 as illustrated in Figure 1 B, the components described are added in the following parts per mass in step A:

20 to 40 parts per mass of the composition 104; and

60 to 80 parts per mass of the second organic solvent,

such that the total parts per mass of the composition and second organic solvent add up to 100.

The composition 104 of Figure 1A refers to one wherein the composition comprises fluororesin with an average particle diameter of 1 mm or more and 5 mm or less and a maximum particle size of 10 mm or less, a dispersant, and organic solvent or residual organic solvent having percentage by mass of 0.2 mass% or less. The composition 104 of Figure 1 A may be in a form of a cake-like material, or more specifically, a dried or hardened solid mass in another example, the composition 104 of Figure 1 A may be in powder form and not aggregated to form the cake-like material.

One of the advantages of the composition 104 of Figure 1A is that transportation problems can be avoided since the hazardous organic solvent in the fluororesin dispersion is removed or substantially removed.

Another advantage of the composition 104 of Figure 1A is that it is able to return to the dispersed state again easily via steps A and B of Figure I B. The size of the fluororesin powder after redispersion in step B of Figure 1 B is 10 mm or less. Yet another advantage is that the redispersion of the composition 104 in step A is performed without using dispersing beads. In addition, a suitable but different solvent (from the first organic solvent) can be used in step A of Figure 1 B. The organic solvent for the redispersion of the composition 104 is not restricted to the first organic solvent.

One of the applications of the composition according to an example of the present disclosure is for the manufacture of high frequency circuit boards. Hence, the fluororesin in the composition 104 of Figure 1A may be perfluoro type fluororesin, which has higher dielectric characteristics. Specifically, the fluororesin can be tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Tetrafluoroethylene-hexafluoropropylene is another choice for the fluororesin because it melts during the heating process. Therefore, the fluororesin may be one or two selected from a group comprising tetrafluoroethyllene-perfluoroalkyl vinyl ether copolymer and tetrafluoroethylene-hexafluoropropylene copolymer.

In another example of the present disclosure, the fluororesin in the composition 104 of Figure 1 A may contain monomers in an amount of 10 mo!% or less for the purposes of improving functions in high frequency circuit boards. For example, the fluororesin may contain itaconic anhydride and 5-norbornene-2,3-dicarboxylic anhydride for improving adhesion of a matrix resin to a substrate of such high frequency circuit boards.

According to an example of the present disclosure, the size of the fluororesin powders in the second fluororesin dispersion 202 of Figure 1 B (after redispersion) is 10 mm or less. When it is 10 mm or more, there may be some negative influence on smoothness of a substrate of a high frequency circuit board, and the dielectric characteristics of the substrate would be affected. This in turn may affect the performance of the high frequency circuit. Such problem affecting the performance of the high frequency circuit becomes significant especially in a multilayer board in which a plurality of substrates is laminated. To obtain a redispersed state of not more than 10 mm, it is required that the average particle diameter in the composition 104 of Figure 1 A is 1 to 5 mm or less and the maximum particle diameter is 10 mm or less. When the average particle diameter is 1 mm to 5 mm, the amount of the dispersant and organic solvent for the redispersion of the second fluororesin dispersion 202 does not adversely affect the electrical characteristics.

In regard to the organic solvent that is used for the first fluororesin dispersion 106 of Figure 1A, an example is to use one that volatilizes until the percentage by mass of the organic solvent in the composition 104 is 0.2% or less under normal pressure or reduced pressure in the case of the application to high frequency circuit boards, organic solvents are usually used based on the solubility in the matrix resin illustrative examples of such organic solvents include MEK (methyl ethyl ketone), toluene, xylene, DMF (dimethyiformamide), NMP (N-methylpyrrolidone), DMAC (dimethylacetamide), CAN (cyclohexanone) and the like. As for the dispersant in the composition 104 of Figure 1 A, an example Is an oligomer of hexafluoropropene. Therefore, the dispersant may be a hexafluoropropylene trimer. The dispersant may comprise one or more surfactant. The amount of the dispersant to be added varies depending on the organic solvent to be used, but may be generally about 1 to 10 parts per mass per 100 parts of the fluororesin. In relation to the dispersing beads for dispersing the first fluororesin dispersion 106 of Figure 1A, glass, ceramic beads and oxide beads may be used. EXAMPLES Preparation of a Dispersion in Example 1 (Ex.1)

25g of tetrafluoroethylene-perfluoroalkylether copolymer (particle diameter D50: 2.1 µm) (fluororesin), 1g of hexafluoropropylene trimer surfactant (dispersant), 75g of methylethylketone (MEK) solvent (organic solvent) and 12.5g of zirconia (Zr) beads as dispersing beads (2mm diameter) were added into a glass jar of 300ml capacity. The glass jar was sealed with an inner cap and jar cap. The sealed glass jar was placed into a paint shaker (Collomix AGIA 200) and shaken for 60 mins. The mixture in the jar is then filtered through 185 micron strainer (an example of the filter 102 of Figure 1A) once to remove the zirconia beads. The particle size of the dispersion obtained was determined to be less than 10 µm by a grind gauge. Preparation of a Dispersion in Example 2 (Ex.2)

The dispersion was prepared as described in Example 1, except that acetone was used as the organic solvent instead of MEK. The particle size of the dispersion obtained was determined to be less than 10 µm by a grind gauge. Preparation of a Dispersion in Example 3

This example is meant as a comparative example. The dispersion was prepared as described in Example 1, except that zirconia beads were not added as dispersing beads. The particle size of the dispersion obtained was determined to be more than 10 µm by a grind gauge. Preparation of a Dispersion in Example 4

This example is meant as a comparative example. The dispersion was prepared as described in Example 1, except that shaking duration was 45 mins instead of 60 mins. The particle size of the dispersion obtained was determined to be more than 10 µm by a grind gauge. Table 1 shows a summary of the results from Examples 1 to 4. The desired results (i.e. particle size less than 10 µm) are found in Examples 1 and 2 while Examples 3 and 4 are comparative examples that did not produce the desired results.

Preparation for Redispersion in Example I

The dispersion obtained by Example 1 above was dried by exposing it to ambient conditions (25°C) for 7 days and leaving the glass jar unsealed in a fume hood to obtain a cake-like material. The cake-like material was confirmed to be dried by subjecting the cake-like material to heat and verifying that the percentage change in mass of the cake-like material to be 0.2% or less. 20g of the cake-like material and 60g of acetone was added into a glass jar of 300ml capacity. The mass of the redispersion solvent to the mass of the cake-like material is 3:1. The glass jar was sealed with an inner cap and jar cap. The sealed glass jar is placed into a paint shaker (Collomix AGIA 200) and shaken for 60mins. The particle size of the dispersion obtained was determined to be less than 10 µm by a grind gauge. Preparation for Redispersion in Example II

The redispersion was prepared as described in Embodiment I, except that MEK was used as the redispersion solvent. The particle size of the dispersion obtained was determined to be less than 10 µm by a grind gauge. Preparation for Redispersion in Example III

The redispersion was prepared as described in Example I, except that the cake-like material used was obtained by drying from Example 2 and MEK was used as the redispersion solvent. The particle size of the dispersion obtained was determined to be less than 10 µm by a grind gauge. Preparation for Redispersion in Example IV

This example is meant as a comparative example. The redispersion was prepared as described in Example I, except that dimethylacetamide was used as the redispersion solvent. The particle size of the dispersion obtained was determined to be more than 10 mm by a grind gauge.

Preparation for Redispersion in Example V

This example is meant as a comparative example. The redispersion was prepared as described in Example I, except that toluene was used as the redispersion solvent. The particle size of the dispersion obtained was determined to be more than 10 mm by a grind gauge.

Preparation for Redispersion in Example VI

This example is meant as a comparative example. The redispersion was prepared as described in Example I, except that toluene was used as the redispersion solvent and the mass of the redispersion solvent to the mass of the“cake-like material” is increased to 4:1. The particle size of the dispersion obtained was determined to be more than 10 mm by a grind gauge. Preparation for Redispersion in Example VII

This example is meant as a comparative example. The redispersion was prepared as described in Example I, except that toluene was used as the redispersion solvent and the redispersion method used was stirring for 60 mins by a Paint Stirrer. The particle size of the dispersion obtained was determined to be more than 10 mm by a grind gauge.

Table 2 below shows successful results of redispersion by using a redispersion solvent that is different from the first dispersion solvent. A successful result is defined as redispersion to below 10 mm marticle size. The successful examples of redispersion are found in Examples I and III, while Examples II, and IV to VII are comparative examples.

Table 2. Summary of Results of Examples I to VII

[Details of Chemicals used]

In the specification and claims, unless the context clearly indicates otherwise, the term “comprising” has the non-exclusive meaning of the word, in the sense of“including at least” rather than the exclusive meaning in the sense of“consisting only of”. The same applies with corresponding grammatical changes to other forms of the word such as “comprise”, “comprises” and so on.

While the invention has been described in the present disclosure in connection with a number of embodiments and implementations, the invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims. Although features of the invention are expressed in certain combinations among the claims, it is contemplated that these features can be arranged in any combination and order.

Claims

1. A composition, comprising:

(i) a fluororesin having an average particle diameter of 1 mm or more and 5 mm or less and a maximum particle size of 10 mm or less;

(ii) a dispersant; and

(iii) an organic solvent, wherein percentage by mass of the organic solvent in the composition is 0.2% or less.

2. The composition according to claim 1 , wherein the fluororesin is one or two selected from a group comprising tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer and tetrafluoroethylene-hexafluoropropylene copolymer.

3. The composition according to claim 1 or 2, wherein the fluororesin comprises a monomer in an amount of 10 mol% or less.

4. The composition according to claim 3, wherein the monomer Is selected from a group comprising itaconlc anhydride and 5-norbornene-2,3-dicarboxyiic anhydride.

5. The composition according to any one of claims 1 to 4, wherein the dispersant is a oligomer.

6. The composition according to claim 5, wherein the oligomer is a hexafluoropropylene tr!mer.

7. The composition according to any one of claims 1 to 6, wherein the organic solvent Is selected from a group comprising MEK (methyl ethyl ketone) and acetone.

8. The composition according to any one of claims 1 to 7, wherein the fluororesin composition is in a form of a powder or a cake-like material.

9. A method of producing a composition according to claim 1 , the method comprising:

(i) a mixing step to mix a fluororesin, a dispersant, an organic solvent and dispersing aid to form a mixture;

(ii) a dispersion step to disperse the fluororesin in the mixture to form a dispersion;

(iii) a filtration step to remove the dispersing aid in the dispersion; and (iv) a drying step to remove the organic solvent present In the filtered dispersion such that percentage by mass of the organic solvent in the composition is 0.2% or less.

10. The method according to claim 9, wherein the mixing step comprises:

(a) mixing the fluororesin, the dispersant and the organic solvent in the following parts per mass:

1 to 40 parts per mass of the fluororesin;

1 to 10 parts per mass of the dispersant; and

50 to 98 parts per mass of the organic solvent,

such that the total parts per mass add up to 100;

(b) adding 10 to 20 parts per mass of the dispersing aid per 100 parts of the fluororesin, the dispersant and the organic solvent.

1 1. A method of producing a fluororesin dispersion, the method comprising:

(i) a mixing step to mix a second solvent to the fluororesin composition according to any one of claims 1 to 9 to form a mixture; and

(ii) a dispersion step to disperse the fluororesin in the mixture without using dispersing aid to form the fluororesin dispersion,

wherein the fluororesin in the fluororesin dipersion has an average particle diameter of 1 mm or more and 5 mm or less and a maximum particle size of 10 mm or less.

12. The method according to claim 11 , wherein the mixing step comprises:

adding 20 to 40 parts per mass of the fluororesin composition and 60 to 80 parts per mass of the second solvent, such the total parts per mass of the fluororesin composition and the second solvent add up to 100.

13. The method according to claim 11 or 12, wherein the second solvent is selected from a group comprising MEK (methyl ethyl ketone) and acetone.