JP3226709B2 - Aramid-polyester laminate, intermediate material thereof and methods for producing them - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to mechanical characteristics, electrical characteristics,
Excellent heat resistance, chemical resistance, impregnation with varnish, insulating oil, etc.
The present invention relates to a novel aramid-polyester laminate particularly preferably used as an electric insulating material in the field of a rotating machine, an intermediate thereof, and a method for producing them.

[0002]

2. Description of the Related Art Conventionally, several kinds of sheets made of aramid (wholly aromatic polyamide) have been developed and used as electric insulating sheets (paper) having excellent heat resistance and electric insulating properties. Among them, there are a paper-like material composed of poly (m-phenylene isophthalamide) pulp and aramid fiber, a paper-like material composed of poly (m-phenylene isophthalamide) pulp and polyethylene terephthalate fiber, and the like.
Aramid paper using such aramid pulp is used for electrical insulation because of the film-like form of the pulp.

[0003] Aramid paper is produced by a usual wet papermaking method, and is subjected to heating and pressurizing (calendering) processing as necessary. Since these aramid papers usually have many voids inside, the dielectric breakdown voltage per thickness (BDV; unit KV / mm) is more inevitable than a homogeneous film having the same thickness. On the other hand, it is excellent in impregnating properties with varnish, insulating oil, etc.

On the other hand, although heat resistance and impregnation are inferior to aramid paper, they are inexpensive. D. V. Is large,
Films such as polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN) are also used as electric insulating materials because of their excellent mechanical properties.

Further, the polyester film and the aramid paper are bonded with an adhesive in order to provide an insulating material having both the heat resistance, the oxidation resistance and the impregnation property of the aramid paper and the excellent electrical insulation and mechanical properties of the polyester film. A laminated multilayer structure sheet is also known.

[0006]

The production of such a multi-layer structure sheet requires a step of applying and laminating an adhesive or laminating with an adhesive tape interposed therebetween, which is not necessarily industrially advantageous. Not a way. Moreover, the use of an adhesive has the disadvantage of impairing the excellent flexibility of the original aramid paper or polyester film. Further, such a multilayer structure sheet is often impregnated with varnish when used, but at that time, there is a problem that voids and cracks are generated since the adhesive is often attacked by the varnish. Therefore, a complicated procedure of confirming the compatibility between the adhesive and the varnish in advance is required, and the varnish that can be used is restricted, which is an obstacle to use.

For this reason, an attempt has been made to bond aramid paper and a polyester film without using an adhesive. For example, Japanese Patent Application No. 5-1753111 discloses that an aramid paper and a polyester film are directly bonded without using an adhesive. A method of thermally bonding has been proposed. However, since the aramid paper and the polyester film have a large gap in heat resistance, the range in which direct bonding can be performed by such a method is limited to a thin polyester film having a thickness of less than 25 μm in consideration of quality stability. In the past, in the pasting with a thick polyester film having a thickness of 25 μm or more which is frequently used in practice, a method using an adhesive is still the mainstream at present.

Accordingly, it is an object of the present invention to provide a laminate in which an aramid paper layer and a polyester film layer are integrally joined without using an adhesive, and a method for producing the same.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, after forming a polyester melt-impregnated layer on the aramid paper bonding surface in advance, a specific condition was obtained. Excellent flexibility, mechanical properties, heat resistance, electrical insulation, impregnation, and chemical resistance even when bonded to a polyester film of any thickness by pressing and heat bonding the polyester film with The present inventors have found that an excellent laminate can be obtained, and have reached the present invention.

That is, the present invention provides a polyester film layer (C layer) via an aramid paper layer (A layer) composed of aramid fiber and aramid pulp via a layer (B layer) in which the surface layer of the layer is melt-impregnated with polyester. layers) being firmly joined allowed aramid - a polyester laminate, B layer and
Polyester of C layer is polyethylene terephthalate or
Polyethylene naphthalate and the layer B and layer C
The invention relates to aramid-polyester laminates in which the ester is the same .

The aramid paper used as the layer A in the present invention is a synthetic paper containing aramid pulp as at least one of the constituent elements.

Aramid pulp is a pulp-like particle having a papermaking property also called “fibrid” made of m-aramid represented by poly (m-phenylene isophthalamide). For example, it can be produced by a wet precipitation method described in JP-B-35-11851.

The above-mentioned aramid is preferably one mainly composed of poly (m-phenylene isophthalamide) which has excellent heat resistance and is hardly oxidized. This aramid is a substance having heat welding property among aramids produced industrially. Aramid pulp is used by adjusting its freeness prior to wet papermaking. The range of freeness of the pulp is preferably selected from 80 to 200 ml in Canadian freeness.

In the layer A (aramid paper layer) of the laminate of the present invention, the aramid fiber mixed and formed with aramid pulp preferably has a fiber length of 3 to 10 mm and a fineness of 0.5 to 5 de. The fiber material may be the same as or different from the pulp. However, the heat resistance is preferably at the same level as that of pulp.
M-aramid fiber represented by phenylene isophthalamide) is most preferred. Of course, another aramid (for example, P-aramid) may be used. Further, other heat-resistant polymers such as aromatic polyetherketone (eg, PEE)
K), a wholly aromatic polyester (arylate) fiber may be used in combination with an aramid fiber, and depending on the application, a polyethylene terephthalate fiber, rayon fiber, phenol fiber, polybenzimidazole (PBI) fiber or the like can be used in combination. .

In the layer A of the laminate of the present invention, the weight ratio between the aramid pulp and the aramid fiber is 1
The range of 0/90 to 90/10 is appropriate, and 30/70
~ 70/30 is particularly preferred. When the content of aramid pulp in the paper is less than 10% by weight, the strength of the aramid paper is significantly reduced. On the other hand, if the content of aramid pulp in the paper exceeds 90% by weight, the varnish impregnability of the paper is undesirably reduced.

When the above-mentioned aramid pulp and aramid fiber are made into a paper, a usual wet paper-making method can be adopted. That is, a predetermined amount of pulp and fiber is made into a dilute slurry dispersed in an aqueous solution, and this is made into a web by a paper machine. The slurry concentration at this time is preferably about 0.01 to 0.5% by weight from the balance between web uniformity and productivity. The web thus obtained can be used after being squeezed and dried, but can also be used after being calendered and adjusted to desired mechanical properties, thickness and density as required. The thickness of the layer A (thickness including the layer B) is 30 to 100.
μm, of which the thickness of the layer B (polyester-impregnated layer) is 5 to 40 μm. The ratio of the thickness of the layer A to the thickness of the layer B is preferably A / B = 2/1 to 10/1.

Meanwhile, the polyester film constituting the C layer of the present invention are films of polyethylene terephthalate and / or polyethylene-2,6-naphthalate is used, melting the homo- or copolyesters containing the above-mentioned components 80 mol% or more Used after film formation. As is well known, the above polyester film is extruded from a T-die in a molten state and is formed into a sheet-like form. Continued
The film is stretched uniaxially or biaxially for the purpose of imparting a desired film thickness, mechanical properties, heat shrinkage, dimensional stability and the like, and is usually subjected to a heat setting treatment or the like. The film used in the present invention is preferably a stretched film, but of course, an unstretched film may be used.

Although the thickness of the polyester film is not particularly limited, it is 12.5 to 350 μm, particularly 25 to 300 μm, from the industrial supply system and the operability of the laminating process.
Are preferred.

As long as the physical properties of the film are not significantly impaired, those containing a small amount of other copolymer components in addition to the above-mentioned homopolymer of polyester can be used.

The polyester film may contain an appropriate amount of an antioxidant, an antistatic agent, a lubricant or the like as long as its properties are not impaired.

[0021] B layer in the laminate of the present invention, Ru is formed by melting impregnating the same polymer and the polyester constituting layer C (the film layer) on the surface layer of the aramid paper constituting the A layer. The layer B (polyester-impregnated layer) has a thickness of 5 to 40 μm and the above A / B = 2/1 to 10 /
It is preferably 1. If the B layer is thinner than this, the adhesive strength at the interface of the finally obtained aramid-polyester laminate is undesirably reduced. On the other hand, when the thickness of the layer B is larger than this, the flexibility is lowered and an aramid paper layer having an excessive thickness is required to secure the impregnation property, which is not preferable.

In the present invention, the method of forming the layer B is not particularly limited.
A method in which the aramid paper used for the layer is overlaid and heated and pressed to melt and impregnate the polyester into the aramid paper. The polyester paper (web) and the aramid paper used in the layer A are laminated or overlapped and heated. A method of applying pressure and melting and impregnating polyester into aramid paper is employed.

These methods are described in detail below.

When the layer B in the laminate of the present invention is formed using a polyester film and aramid paper,
The thickness of the polyester film used is preferably 5 μm or more in order to maintain the thickness of the layer B.

After the polyester film and the aramid paper are dried, they are dried at 150 to 350 ° C.
The polyester film is melted by heating at 00 to 300 ° C., and the polyester is impregnated into the layer A by applying a linear pressure of 50 kg / cm or more. When the temperature is lower than 150 ° C., the impregnation is not sufficiently performed, which is not preferable. Also,
If the temperature is higher than 350 ° C., decomposition of the polyester component becomes remarkable, which is not preferable. In addition, a linear pressure of 50 kg / cm or more is required to achieve an improvement in impregnation.

The polyester film and the aramid paper may be impregnated directly under the above conditions, or they may be preliminarily bonded and integrated beforehand, and then impregnated under the above conditions to form the B layer. Good. In the latter case, the temporary bonding and integration can be performed, for example, by heating and pressing under a temperature and pressure of 150 to 220 ° C. and a linear pressure of 50 Kg / cm. Also,
In the impregnation treatment, heating and pressurization may be performed simultaneously or sequentially.

When the layer B in the laminate of the present invention is formed using a polyester paper (web) and aramid paper, a base paper obtained by combining the aramid web and the polyester web on one side in wet papermaking is used. Is preferred. In this case, the aramid web should keep the above-mentioned composition, but the aramid web obtained in this way has sufficient strength, and the polyester web to be milled therewith is not limited in strength.
%, Or 100% polyester pulp (fibrid). Of course, it may be formed of a mixture of polyester short fibers and pulp in any ratio.

The combined web thus obtained is squeezed,
After drying, 150-350 ° C, preferably 200-3
Heat to 00 ° C to melt the polyester and apply a linear pressure of 5
The layer A is impregnated by applying a pressure of 0 kg / cm or more. At this time, when the temperature is lower than 150 ° C., the impregnation is not sufficiently performed, which is not preferable. On the other hand, when the temperature is higher than 350 ° C., the decomposition of the polyester component becomes remarkable, which is not preferable. In order to achieve an improvement in impregnation, the linear pressure is 50K.
g / cm or more is required.

In this impregnation operation, heating and pressurization may be performed simultaneously, or after heating, pressurization may be performed in a press zone of less than 150 ° C. However, when the latter sequential impregnation operation is employed, the web temperature at the press zone entry side should be maintained at 150 to 350 ° C. In order to maintain the thickness of the layer B in the laminate of the present invention within a predetermined range, the basis weight of the polyester web layer to be ground is 5 g.
/ M ² or more.

In any case, after heating and pressurizing treatment in the melt impregnation operation, the mixture is cooled at a temperature lowering rate of 100 ° C./min or more. If the cooling rate is lower than this, the polyester is liable to be crystallized, and the flexibility is undesirably deteriorated.

The A layer (intermediate material) with the B layer thus obtained and the polyester film to be the C layer are integrally laminated and firmly joined to produce the laminate of the present invention. The thickness of the layer B is preferably 5 to 40 μm, and the thickness of the aramid paper layer (layer A) including the layer B is 30 to 100 μm.
Is as described above.

The laminate of the present invention includes a laminate in which the layer A is disposed on one side of the layer C as described above, and a laminate in which the layer A is disposed on both sides of the layer C. After the A layer and the C layer with the B layer are laminated in a desired laminated structure such that the layers are in contact with each other, bonding is performed under the following conditions.

The final bonding temperature in the present invention is 15
0 to 250 ° C. The temperature at the time of final bonding is 250 ° C
If it exceeds, the layer B prepared in advance is destroyed and the interfacial adhesion of the obtained laminate is undesirably reduced. Meanwhile, 1
If the temperature is lower than 50 ° C., the adhesiveness between the layer B and the layer C is undesirably reduced.

The final bonding pressure in the present invention is set to a linear pressure of 50 kg / cm or more. If it is lower than this pressure,
It is not preferable because the interfacial adhesion of the obtained laminate is reduced. Although there is no particular upper limit for the pressure, the upper limit is usually 400 Kg / cm in a normal case from the viewpoint of equipment.

After performing the heating and pressurizing treatment in the above-mentioned laminating operation, the laminate is cooled at a temperature lowering rate of 100 ° C./min or more. If the cooling rate is lower than this, the polyester is liable to be crystallized, and the flexibility is undesirably deteriorated.

The equipment for performing the impregnation and lamination is not particularly limited, and any equipment can be used as long as it can apply a predetermined temperature and pressure. For example, when heating and pressurization are performed simultaneously, It can be easily implemented by using a pair of a heating roller and a cooling roller, and passing the intermediate material and the polyester film one on top of the other. When heating and pressurization are performed sequentially, it can be easily performed by using a heating furnace, a pair of pressurizing rollers and a cooling roller.

In the present invention, in order to improve the thermal adhesion and impregnation between the polyester and the aramid paper, the aramid paper and / or
Alternatively, the polyester film may be subjected to a surface treatment. Further, if necessary, the aramid paper may be subjected to pressure and heat bonding in a state of containing water or a solvent aqueous solution.

Aramid paper impregnated with polyester (intermediate material)
The method of laminating the polyester film with the polyester film can be appropriately selected depending on the use and purpose of the laminate. For example, two-layer bonding of the aramid paper (intermediate material) and a polyester film is suitable for the purpose of suppressing the generation of fluff on the aramid paper while making use of the impregnating property and air permeability of the aramid paper. For the purpose of suppressing the oxidation of the film surface by making use of the electrical insulation properties of the polyester film, a laminate having a three-layer structure in which the film is sandwiched by the aramid paper (intermediate material) is suitable.

[0039]

According to the present invention, a sheet-like aramid-polyester laminate having flexibility, excellent in mechanical properties, heat resistance, electrical insulation, impregnation of insulating varnish, etc., chemical resistance, etc., can be arbitrarily prepared. And in an industrially advantageous manner without the use of adhesives.

Such an aramid-polyester laminate is suitably used as an electrical insulating material for transformers, motors, generators and the like.

[0041]

The present invention will be described in detail below with reference to examples and comparative examples. These show specific examples of the present invention, and do not limit the present invention at all.

The evaluation method in the present invention is as follows. (A) Dielectric breakdown voltage (BDV): Measured with an AC voltage according to JIS-C2111 (unit: KV / mm). (B) Adhesiveness of the laminated paper: Wrinkles on the surface after hot pressing and the state of adhesion were visually determined. In the table, ○: good, Δ: slightly good, ×: bad. (C) Tensile strength: based on JIS-P8113.

Examples 1 to 5 and Comparative Examples 1 to 3 (1) Production of Aramid Paper A polymer of poly (m-phenylene isophthalamide) was produced by the interfacial polymerization method described in JP-B-47-10863. It was dissolved in N-methyl-2-pyrrolidone and had an intrinsic viscosity (IV) of 1.35, which did not include inorganic salts.

The polymer was made into a fiber based on the wet spinning method described in JP-B-48-17551. The fiber stretched in boiling water and further stretched on a hot plate had a tensile strength of 4.5 g / de and an elongation of 18%. This was cut to a length of 6 mm.

Similarly, the above-mentioned polymer was replaced with JP-B-52-15.
Pulp (fibrid) was prepared using a precipitation apparatus (150 mm in diameter) described in JP-A-1621. This was beaten with a disc refiner. The freeness was 110 ml in Canadian freeness.

These pulp and fibers are mixed in a weight ratio of 60/40, and the mixture is mixed with a Fordlinia paper machine (fourd line paper machine).
To make a wet paper having a width of 100 cm. The wet paper was squeezed and dried. The basis weight of the obtained dried paper is 37 g
/ M ² .

(2) Production of Aramid-Polyester Paper Aramid wet paper was produced using a fourdrinier according to the above (1), and then produced on the wet paper using a circular paper machine. A wet paper made of polyethylene terephthalate fiber having a length of 6 mm and having a dry basis weight of 18 g / m ² was laminated, and then dried. The basis weight of the obtained dried paper was 55 g / m ² .

(3) Production of Aramid Paper-Polyester Film Temporary Adhesive When the B layer is formed using a polyester film for the purpose of comparing the B layer formation conditions with the aramid-polyester composite paper, the following method is used. Then, a temporary adhesive between aramid paper and a polyester film was prepared.

That is, aramid paper having a basis weight of 37 g / m ² prepared according to the above (1), a width of 90 cm and a thickness of 2
After laminating one 5 μm polyethylene terephthalate film and drying at 200 ° C., the film is passed through a pair of rollers heated to 200 ° C. at a speed of 25 m / min under a linear pressure of 200 kg / cm. Immediately after cooling with a cooling roller, a wound temporary adhesive was obtained. The cooling rate at this time was equivalent to 3400 ° C./min.

(4) Preparation of Aramid Paper-Polyester Impregnated Layer (Layer B) The aramid paper having the polyester prepared in (2) and (3) above on one side is passed through a heating furnace at a temperature shown in Tables 1 and 2. After heating at 130 ° C. while maintaining the paper temperature, a linear pressure of 200 kg / cm was applied between the pair of rollers at a speed of 25 m / min, and then a cooling rate of 3000 ° C./min And cooled.

(5) Production of Aramid-Polyester Laminate Aramid paper impregnated with polyester on one side prepared in (4) above and a 250 μm polyethylene terephthalate film were impregnated with the polyester so that the polyester layer was in contact with the film. Laminated in three layers so as to sandwich the polyethylene terephthalate film between two sheets of aramid paper,
200K between a pair of rollers at the temperatures shown in Tables 1 and 2.
g / cm at a linear pressure of 25 m / min.
Immediately after cooling with a cooling roller, the film was wound up. The cooling rate at this time was equivalent to 3400 ° C./min.

The bonding state of the laminate thus produced was evaluated by visual observation and cross-sectional observation with an electron microscope. The results are shown in Tables 1 and 2.

[0053]

[Table 1]

[0054]

[Table 2]

Comparative Example 4 The aramid paper obtained in the above (1) and a 250 μm polyethylene terephthalate film were laminated in three layers so that the aramid paper sandwiched the polyethylene terephthalate film, and had a linear pressure of 200 kg / cm and a paper passing speed. Thermal bonding was performed by passing between a pair of heating rolls at 25 m / min. The temperature of the heating roll is 150 ° C., 200
C., 250.degree. C. and 300.degree. 150 ° C as a result
At 200 ° C. and at 200 ° C.
At a temperature of 300 ° C. or 300 ° C., the polyethylene terephthalate film was melted and no good laminate was obtained.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (5)

(57) [Claims] 1. An aramid paper layer (A layer) composed of aramid fiber and aramid pulp, and a polyester film layer (C layer) via a layer (B layer) in which the surface layer of the layer is melt-impregnated with polyester. A firmly bonded aramid-polyester laminate comprising a layer B and a layer C polyester
Is polyethylene terephthalate or polyethylene naph
Tarate, and the polyester in the B layer and the C layer are the same
An aramid-polyester laminate . 2. Aramid fiber and aramid pulp are composed of poly (m-phenylene isophthalamide), and
The layer is composed of 10 to 90% by weight of aramid fiber, 9 of aramid pulp
0.4 to 1.0 g / density composed of 0 to 10% by weight
The aramid-polyester laminate according to claim 1, which is a wet paper product of cm ³ . 3. The aramid-polyester laminate according to claim 1, wherein the thickness of the layer B is 5 to 40 μm, and the thickness of the aramid paper layer including the layer B is 30 to 100 μm. 4. A polyethylene terephthalate is provided on a surface layer of an aramid paper layer (A layer) composed of aramid fiber and aramid pulp.
The intermediate material for producing an aramid-polyester laminate according to claim 1, wherein a layer (layer B) impregnated with tartrate or polyethylene naphthalate is melt-impregnated. 5. A wet papermaking of a mixture of (a) 10 to 90% by weight of aramid pulp and 90 to 10% by weight of aramid fiber using water as a medium, and (b) polyester pulp and polyester pulp on one side of the obtained aramid paper. And / or after laminating a wet paper made of polyester fiber having a basis weight of 5 g / m ² or more and drying and removing water, the polyester is heated and pressurized at a temperature of 150 to 350 ° C. and a pressure of 50 kg / cm or more. After the aramid paper is melt-impregnated or the obtained aramid paper is dried, a polyester film having a thickness of 10 μm or more is placed on one side of the obtained dry paper, and a temperature of 150 to 350 ° C. and a temperature of 50 Kg / After heating and pressurizing at a pressure of not less than 1 cm, the polyester is melt-impregnated into the aramid paper, and then cooled at a temperature lowering rate of 100 ° C./min or more. Create an aramid paper was impregnated into a polyester surface and thereafter combined overlapping and (d) the polyester impregnated aramid paper and a polyester film such polyester layer is in contact with each other, then,
(E) After heating and pressurizing at a temperature of 150 to 250 ° C. and a pressure of 50 kg / cm or more to weld the polyester film layer, (f) cooling at a temperature lowering rate of 100 ° C./min or more. A method for producing an aramid-polyester laminate , wherein the polyester-impregnated aramid paper and
The polyester of the polyester film is polyethylene
Terephthalate or polyethylene naphthalate,
And the polyester-impregnated aramid paper and the polyester foil.
Aramid-polyester wherein the polyester of the film is the same
A method for producing a tellurium laminate .