JP2008196059A - Process release paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide process release paper having good releasability, dimensional stability and air permeability, particularly the process release paper suitable for use in prepreg composed of reinforcing fibers such as carbon fibers without causing lifting and peeling or blistering in heat-treating processing. <P>SOLUTION: The process release paper comprises a release agent in at least one surface of base paper. The release agent is composed of a silicone emulsion and the process release paper has ≤300 s air permeability according to JIS P 8117. The base paper preferably has ≥400 ml Canadian standard freeness after disintegration according to JIS P 8121 and the top surface of the base paper is preferably directly coated with the release agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a process release paper, particularly a process release paper suitable for use with a prepreg composed of reinforcing fibers such as carbon fibers.

  Composite products made of various reinforcing fibers such as carbon fiber and glass fiber are lightweight and have high hardness, so they are widely used as sports / leisure products such as fishing rods, tennis rackets, golf clubs, and aircraft wings. However, the intermediate base material used at the time of molding this composite product is called a prepreg. This prepreg is manufactured by impregnating a reinforcing fiber assembly with a thermosetting resin such as an epoxy resin, a phenol resin, or a bismaleimide resin on a process release paper and semi-curing it by heat treatment.

  The process release paper is required to exhibit appropriate release characteristics with respect to the prepreg. That is, when the process release paper is peeled off when the sheet-like prepreg is cut into a desired pattern, the prepreg becomes difficult to handle, and the workability thereof is lowered.

  Furthermore, in the process from the prepreg manufacturing process to the middle of the composite product molding process, the process release paper is under tension, and during the heat treatment for semi-curing and during storage and transportation before the composite product molding process, Although the temperature and humidity also change, since the prepreg itself has almost no dimensional change due to temperature and humidity, the process release paper is also required to have excellent dimensional stability. If the dimensional stability of the process release paper due to heating and humidification is low, the process release paper will partially float from the prepreg, and the surface of the process release paper will be transferred to the surface of the prepreg that comes into contact. Is generated in the prepreg, which causes a problem that the strength of the molded body is lowered and the appearance is impaired.

  One of the means to suppress the peeling of the process release paper from the prepreg is to increase the release force of the process release paper. There's a problem.

  In Patent Document 1, a moisture-proof layer is provided on both surfaces of the base paper and a release layer is provided on the moisture-proof layer to obtain a predetermined low moisture permeability so that good dimensional stability can be achieved even if the temperature and humidity change. Proposals have been made. However, although moisture absorption and release is reduced, air permeability is also lost, so even if the moisture in the process release paper evaporates during heat treatment in the prepreg manufacturing process, it will not come off on the surface of the process release paper, and this will cause floating from the prepreg. There has been a problem of occurrence of blisters and blistering (flame) in the process release paper itself.

Glassine paper, which is widely used as process release paper, is highly beaten before papermaking and has a high fiber-to-fiber bond because it prevents the release agent from penetrating into the paper and leaves the release agent component on the surface. The fiber is crushed by the treatment to increase the density, and the dimensional stability is poor. In addition, there is a method of providing a polyethylene resin layer by extruding and melting on high-quality paper, etc., or providing a sealing layer with inorganic pigments such as clay and calcium carbonate, acrylic resin, etc. There was a problem that the water in the release paper during the heat treatment evaporated to become water vapor and remained on the paper surface, and blisters were generated.
JP 2005-220482 A

  In view of the present situation, the present invention has excellent peelability, dimensional stability, and air permeability, and is used for prepregs made of reinforced fibers such as carbon fiber and other process release papers that do not cause floating or blistering in heat treatment. It is an object of the present invention to provide a suitable process release paper.

  The present invention is a process release paper containing a release agent on at least one surface of a base paper, wherein the release agent is made of a silicone emulsion and has an air permeability of 300 seconds or less according to JIS P 8117. It relates to a process release paper. In addition, since the process release paper of patent document 1 has a moisture-proof layer, it does not satisfy low air permeability, ie, high air permeability as mentioned above.

  The base paper preferably has a Canadian freeness of 400 ml or more after disaggregation according to JIS P 8121, and the release agent is preferably applied directly onto the base paper.

  In the present invention, by using a silicone emulsion as a release agent to obtain a process release paper having a predetermined low air permeability (high air permeability), the release agent has become familiar with the pulp fibers and the pulp surface seems to be coated. It is in a state. For this reason, moisture absorption and release of pulp fiber is suppressed by the silicone emulsion, so that while maintaining the releasability, it has excellent dimensional stability and good air permeability. Even if the water vapor evaporates, water vapor is released from the paper surface to the outside, so that no floating from the prepreg or blistering of the process release paper itself occurs.

  The base paper in the process release paper of the present invention is not particularly limited. Chemical pulps such as: thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP), refiner ground pulp (RGP), chemiground pulp (CGP), thermoground pulp (TGP), groundwood pulp (GP), Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW) and other mechanical pulp; Deinking Pulp (DIP), West Pulp (WP) and other chemical pulp and mechanical pulp-derived waste paper pulp It is done.

  The base paper preferably shows 400 ml or more in order to allow the silicone emulsion described below to be blended with the pulp fiber and hardened at the Canadian standard freeness (hereinafter referred to as freeness) after disaggregation according to JIS P8121. The upper limit is not limited and may be unbeaten. If it is less than 400 ml, the release agent will not be able to penetrate into the gaps between the fibers and sufficient dimensional stability will be difficult to obtain. Therefore, the prepreg may be lifted off due to changes in temperature and humidity during the heating process, storage and transportation. May occur.

  At the time of papermaking, inorganic pigments such as calcium carbonate, clay, talc, silica, and titanium oxide can be appropriately used as fillers, and paper strength enhancers, fixing agents, yield improvers, and the like can be appropriately used as papermaking chemicals.

The basis weight of the base paper is not particularly limited, preferably in the range of 50 to 250 g / ^{m 2,} the range of 70~200g / ^{m 2} is more preferable. If it is less than 50 g / m ² , the strength of the base paper will be reduced, scratches on the surface may be transferred when used as cut paper or process release paper, and the semi-cured prepreg may be bent unintentionally, resulting in poor handling. There is. When it exceeds 250 g / m ² , it becomes difficult to penetrate the release agent into the base paper, and the followability to the prepreg is inferior, so that the process release paper tends to float from the prepreg during winding.

  As the paper machine for making the base paper, each paper machine such as a circular net, a long net, a short net paper machine, and a twin wire can be used, and the paper can be made by a drying method such as a Yankee dryer or a multi-cylinder dryer. A long-mesh Yankee paper machine that can provide excellent base paper is particularly preferable. The drying method using a Yankee dryer is different from the drying method using a general multi-cylinder dryer, and wet paper is attached to the cylinder surface for drying. Therefore, the shrinkage of the paper during drying can be reduced, and the dimensional stability is excellent. Therefore, even when used as a process release paper, expansion and contraction due to heat treatment and temperature / humidity changes are suppressed, and floating and peeling from the prepreg are further reduced.

  In the conventional process release paper, a sealing layer is provided between the base paper and the release layer to suppress the penetration of the release agent into the paper. No stop layer is required. Furthermore, since the moisture-proof layer described in Patent Document 1 is not provided in the process release paper of the present invention, it is preferable that the below-described release agent is applied directly on the base paper.

  In the present invention, it is preferable not to provide the sealing layer in order to achieve good air permeability. However, if the air permeability according to JIS P 8117 of the process release paper is within 300 seconds, A stopper may be applied. The sealing agent used in the sealing layer is not particularly limited, and for example, polypinyl alcohol-based water-soluble resin, acrylic resin-based emulsion, and the like can be used.

  There are no particular restrictions on the method for applying the sealant, but it can be applied using a known coating machine such as a size press, air knife, roll coater, bar coater, comma coater, blade coater, etc. .

  In general, silicones used as release agents in process release papers are classified into solvent-type, emulsion-type, and solvent-free types by type, and by reaction type, condensation-reaction type, addition-reaction type, UV-curing type, and electron beam-curing type. It is divided into. The solvent type includes a condensation reaction type and an addition reaction type that are cured by heat, and the solventless type includes an addition reaction type, an ultraviolet curing type, and an electron beam curing type. However, in the present invention, the sealing is not performed or the sealing effect is hardly exhibited. When a solvent-type or solvent-free silicone is used as a release agent for this, the release agent is contained in the pulp fiber. It penetrates deeply and does not function as a release agent, resulting in poor peelability.

  For this reason, a silicone emulsion is used as a release agent in the present invention. As a result, even if a release agent is applied to the base paper that is not sealed or has little effect of sealing, penetration into the pulp fiber is suppressed and the release agent component remains on the surface. Therefore, good peelability can be maintained.

  The silicone emulsion used in the present invention is an emulsion obtained by dispersing silicone in water. The silicone is not particularly limited. For example, Si-H group-containing silicone, dimethylpolysiloxane, methylphenylpolysiloxane, alkoxy group-containing silicone, silanol group-containing silicone, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, etc. Silicone oil, vinyl silicone, polyether modified silicone, polyglycerin modified silicone, amino modified silicone, epoxy modified silicone, mercapto modified silicone, methacryl modified silicone, carboxylic acid modified silicone, fatty acid ester modified silicone, alcohol modified silicone, alkyl modified silicone, Examples include modified silicones such as fluoroalkyl-modified silicones and photopolymerizable functional group-modified silicones. These silicones can be used alone or in combination of two or more. In addition, as a method of curing the silicone to improve the peelability, addition reaction with Si-H group-containing silicone and vinyl silicone, condensation reaction with Si-H group-containing silicone and silanol group-containing silicone, photopolymerizable functional group modification Although there are UV reactions with silicone, etc., the addition reaction with Si-H group-containing silicone and vinyl silicone is easy to handle without generating by-products and is preferable from the viewpoint of curability.

Is not particularly restricted but includes a coating amount after drying of the release agent is preferably in the range of 0.1 to 10 g / ^{m 2,} the range of 0.3 to 5 g / ^{m 2} is more preferable. If the coating amount is less than 0.1 g / m ² , it may cause peeling failure, and if it exceeds 10 g / m ² , it may not only be uneconomical but also cause curing failure of the release agent.

  Coating or impregnation is performed so that the release agent is contained in the base paper, but the coating method is not particularly limited. For example, a known coating machine such as an air knife, a roll coater, a bar coater, a comma coater, or a blade coater is used. Can be applied. In addition, when a sealing agent or a release agent is applied to one side of a base paper made with a long-mesh Yankee paper machine, it is preferable because the flatness of the prepreg transferred is improved by applying to a glossy surface.

  The process release paper of the present invention is disclosed in J. TAPPI No. It is preferable that the Gurley stiffness according to 40 is 1.8 to 7.0 mN (longitudinal direction). If it is less than 1.8 mN, the process release paper tends to be wrinkled because it is not stiff, and the semi-cured prepreg is unintentionally bent, resulting in poor handling. If it exceeds 7.0 mN, the followability with respect to the prepreg is poor, and floating off due to an external force is likely to occur during processing steps, transportation, and the like.

  In addition, for the process release paper that was cut to 100 mm × 100 mm after being left for 24 hours under conditions of 23 ° C. and 50% RH, the area was completely dried by heating at 110 ° C. for 10 minutes, and under the conditions of 23 ° C. and 50% RH. In the area after standing for 2 hours, the changed area dimensional change rate is preferably 1.00% or less, so that the prepreg is not lifted off due to changes in temperature and humidity during the heating process, storage and transportation. It will be a thing.

  The process release paper of this invention coat | covers the single side | surface or both surfaces of the prepreg which consists of a reinforced fiber, and peels from a prepreg when performing desired shaping | molding using a prepreg. The process release paper of the present invention is a sheet with a constant width and pitch, in particular, a carbon fiber wound in a cheese shape or a carbon fiber aligned and stored in a can etc. so as not to be twisted and shaped through a guide. It is most suitable for coating a carbon fiber prepreg made of a resin and impregnated with a resin.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Examples 1-16 and Comparative Examples 1-4
The number of parts of each chemical is shown in parts by weight based on the active ingredient, and the weight of rice and the coating amount are shown on a dry weight basis.

(1) Base paper Each pulp was blended at a ratio (weight ratio) of LBKP: NBKP of 70:30. Each pulp was measured according to JIS P 8121 using a Canadian freeness measuring device (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the freeness shown in Table 1 was obtained. The freeness of the whole pulp was as shown in Table 1. As the paper machine, a long net Yankee paper machine or a long net multi-cylinder paper machine was used, and the paper was made so as to have the rice tsubo of Table 1.

(2) Sealing layer About what provided the sealing layer, polyvinyl alcohol (Kuraray Co., Ltd. product number: PVA117) was coated with a size press at the coating amount shown in Table 1.

(3) Release agent Each release agent was coated on the front and back of each base paper at 1.5 g / m ² with a bar coater, and then dried and cured at 140 ° C. for 20 seconds.
“Emulsion”: 100 parts of a silicone emulsion (manufactured by Shin-Etsu Chemical Co., Ltd., product number: SM-3951) and 2.5 parts of a platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., product number: CAT-PM-10A) are mixed and coated. did.
"Solvent-free": Solvent-free silicone (manufactured by Shin-Etsu Chemical Co., Ltd., product number: KNS-320) 100 parts and platinum-based catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., product number: CAT-PL-56) are mixed and coated. did.
“Solvent”: 100 parts of solvent silicone (manufactured by Shin-Etsu Chemical Co., Ltd., product number: KS-847) and 1 part of platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., product number: CAT-PL-50T) were mixed and coated.

Process release paper evaluation (1) Air permeability: Measured according to JIS P 8117 using a Gurley densometer (manufactured by Kumagai Riki Kogyo Co., Ltd.).
(2) Gurley stiffness (longitudinal direction): A Gurley stiffness measuring instrument (manufactured by Toyo Seiki Seisakusho) was used. TAPPI No. Measured according to 40.

(3) Peelability: A standard tape (Nitto Denko, No. 31B, 40 mm width) is attached to the release paper in each step with a length of 200 mm, and one reciprocating press with a 2 kg rubber roller. The above samples were evaluated by the strength when peeled 180 ° at a rate of 300 mm / min with a universal tensile testing machine (manufactured by Toyo Seiki Seisakusho, Strograph V1-C) after 30 minutes.
A: 5 to 50 gf / 40 mm, which is favorable.
X: Since it exceeds 50 gf / 40 mm, a peeling defect is considered. (Does not peel or delamination of process paper)
-: It is less than 5 gf / 40 mm, it is considered that the prepreg is not supported, and cannot be evaluated.

(4) Area dimensional change rate: The area of the process release paper cut to 100 mm × 100 mm after being left for 24 hours under the condition of 23 ° C. and 50% RH and heated to 110 ° C. for 10 minutes, and 23 ° C. 50 In the area after being left for 2 hours under the condition of% RH, the area dimensional change rate (%) when changed was measured.
Area dimensional change rate (%) = [(area of 23 ° C., 50% RH−area of absolutely dry state (23 ° C., dry)) / area of absolutely dry state (23 ° C., dry)] × 100

(5) Heat floating off: After producing a prepreg of carbon fiber using release paper in each step, the carbon fiber prepreg was treated at 100 ° C. for 1 minute, and the floating off of the prepreg was visually evaluated.
(Double-circle): The float was not seen at all.
◯: Slight lifting was observed, but it was at a satisfactory level.
X: The float was large and was peeling off.
-: No problem due to peeling failure

(6) Floating and peeling off external force: After producing a prepreg of carbon fiber using release paper in each step, bending in the winding direction was performed to visually evaluate the floating off of the prepreg.
(Double-circle): The float was not seen at all.
◯: Slight lifting was observed, but it was at a satisfactory level.
X: The float was large and was peeling off.
-: No problem due to peeling failure

(7) Pre-preg workability: After manufacturing a carbon fiber prepreg using each process release paper, the workability was evaluated, for example, whether it was bent by gravity by holding it in hand.
A: Slight and stable.
〇: Slightly connected, but there was no problem in workability.
X: Depending on how it is held, it bends unintentionally and workability is poor.
Each evaluation result is shown in Table 1.

  From Table 1, the process release papers obtained in Examples 1 to 16 were excellent in air permeability, peelability and dimensional stability, and hardly peeled off due to heating and external force. In No. 2 and No. 2, there was a lot of floating peeling due to heating, and in Comparative Examples 3 and 4 where the release agent was not a silicone emulsion, there was a problem in peelability.

The present invention provides a process release paper suitable for use with a prepreg composed of reinforcing fibers such as carbon fibers.

Claims (2)

A process release paper containing a release agent on at least one side of a base paper,
The release agent comprises a silicone emulsion,
Process release paper characterized by air permeability according to JIS P 8117 being 300 seconds or less. The base paper has a Canadian standard freeness of 400 ml or more after disaggregation according to JIS P 8121,
The process release paper according to claim 1, wherein the release agent is directly applied onto a base paper.