JP6212461B2 - Polyester resin foam sheet and method for producing the same - Google Patents

Description

  More particularly, the present invention relates to a polyester resin foam sheet used as a core material of a fiber-reinforced composite, and a polyester resin foam sheet suitable for the core material. The present invention relates to a manufacturing method for manufacturing.

Conventionally, sheet-like fiber reinforced resin materials such as a mixture sheet of short fibers for reinforcement such as glass fiber and carbon fiber and a resin, a prepreg sheet in which a thermosetting resin is impregnated and supported on a woven fabric or a nonwoven fabric made of the above fibers, have been used. Widely used as a forming material for the bodies of ships and freight cars.
In recent years, it has been studied to fabricate a fiber reinforced composite having both excellent strength and light weight by laminating and integrating such a sheet-like fiber reinforced resin material on a core material made of a resin foam. (See Patent Document 1 below).
The fiber reinforced composite produced in this way has a fiber reinforced resin layer with excellent strength due to the fiber reinforced resin material on the surface, and a lightweight resin foam is used for the core material. Therefore, applications are expanding in fields where high mechanical strength and light weight are required, such as wind turbine blades for wind power generation, housings for electronic devices, and automobile parts.

JP 2014-028920 A

The fiber reinforced composite is required to exhibit excellent adhesiveness between the fiber reinforced resin layer and the core material.
For this reason, various efforts have been made so far, but a method for satisfying such a demand has not been sufficiently established.
One object of the present invention is to satisfy such a demand and to provide a polyester resin foam sheet useful for a core material that can exhibit excellent adhesive strength with a fiber reinforced resin layer. Is an issue.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor can easily exhibit excellent adhesiveness with the fiber reinforced resin layer by improving the surface state of the resin foam as a core material. For foam sheets made of hard resin such as polyester resin, it is easy to prepare the cell membrane constituting the sheet surface in a specific state, and excellent between the fiber reinforced resin layer The inventors have found that it is easy to exert adhesiveness and have completed the present invention.

  The present invention relating to a polyester resin foam sheet for solving the above problems is a polyester resin foam sheet used as a core material of a fiber-reinforced composite, wherein the cell membrane forms a cell membrane in the sheet thickness direction. It is a polyester-based resin foam sheet that is recessed inside to form irregularities on the sheet surface.

  In addition, the present invention relating to a method for producing a polyester resin foam sheet for solving the above-mentioned problems includes a sheet preparation step of producing a polyester resin foam sheet by extrusion foaming a polyester resin composition containing a foaming agent. A method for producing a polyester-based resin foam sheet, wherein in the sheet preparation step, the surface of the polyester-based resin foam sheet is cooled to cause the bubble film on the surface of the sheet to sag inward in the sheet thickness direction. This is a method for producing a polyester resin foam sheet for producing a polyester resin foam sheet in which irregularities are formed on the sheet surface by depression.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester-type resin foam sheet which exhibits the outstanding adhesive force between fiber reinforced resin materials using the unevenness | corrugation of a surface is provided.

The schematic perspective view which showed the one aspect | mode of the fiber reinforced composite_body | complex. The schematic perspective view which showed the one aspect | mode of the polyester-type resin foam sheet used as a core material of a fiber reinforced composite. The expanded sectional view which showed typically the mode of the sheet | seat surface vicinity of the polyester-type resin foam sheet. The expanded sectional view which showed the mode of the smoothing process typically. The figure which showed the surface depression state (X) of the resin foam sheet of Example 2, and the surface depression state (Y) of the resin foam sheet of Example 8. FIG.

Embodiments of the present invention will be described below.
First, the fiber reinforced composite will be described.
The fiber reinforcement of the present embodiment is obtained by laminating and integrating a fiber reinforced resin layer on the surface of a core material.
In addition, in FIG. 1, a long plate-like thing is illustrated as a fiber reinforced composite, and in FIG. 2, the elongate strip-shaped resin foam used as a core material of such a fiber reinforced composite is illustrated. Yes.

The fiber reinforced composite A is a sheet-like fiber reinforced composite that has a rectangular shape in plan view similar to the core material A1 on both sides of a core material A1 that is made of a resin foam sheet having a rectangular shape in plan view as shown in the figure. A material (fiber reinforced resin sheet) is laminated and a fiber reinforced resin layer A2 is provided on both sides.
The fiber reinforced resin sheet constituting the fiber reinforced resin layer A2 includes a resin and reinforcing fibers.
The reinforcing fiber of the fiber reinforced resin sheet may be a fiber woven fabric to constitute a base sheet of the fiber reinforced resin sheet, or may be dispersed in the fiber reinforced resin sheet as a short fiber. .
The resin foam sheet constituting the core material is a resin foam sheet made of a polyester resin composition. In this embodiment, the polyester resin foam sheet obtained by extrusion foaming a polyester resin composition containing a foaming agent. (Hereinafter also simply referred to as “foamed sheet”).

In the foam sheet constituting the core material, the bubble film forming the sheet surface is recessed on the inner side in the sheet thickness direction so that the sheet surface is uneven.
Since the core material A1 has such unevenness on the surface, the core material A1 can exhibit an anchor effect with the fiber reinforced resin layer A2, and exhibits excellent adhesiveness with the fiber reinforced resin layer A2. be able to.
In the case where the fiber reinforced resin sheet has a fiber woven fabric or the like as a base sheet, and the fiber reinforced composite is a three-dimensional one instead of the one illustrated in FIG. 1, the core material and the fiber reinforced resin sheet If there is not enough slip, the fibers of the base sheet are likely to be disturbed in the finished state of the fiber reinforced composite, and the appearance may not be improved, and in some cases, the strength may vary.
Therefore, the core material before being laminated on the fiber reinforced resin sheet preferably has a surface roughness of 1 μm to 10 μm, more preferably 1 μm to 5 μm, and more preferably 1 μm to 5 μm. It is particularly preferred that
Unless otherwise specified in the present specification, the “surface roughness” means the arithmetic average roughness (Ra) defined in JIS B0601-2013, and is obtained by the following method. Means.

(How to determine surface roughness (Ra))
The surface roughness was measured according to JIS B0601: 2013.
Specifically, the surface roughness was measured using “Double Scan High Precision Laser Measuring Equipment LT-9500, LT-9010M” manufactured by Keyence Co., Ltd. as a measuring device, and “Non-made” manufactured by Combs Co., Ltd. as data processing software. Measurement was performed using a “contact contour shape roughness measurement system MAP-2DS”.
Regarding the measurement conditions, the measurement range is set to 18000 μm, the measurement pitch is 5 μm, the measurement speed is 1000 μm / second, the evaluation length is 12.5 mm, the reference length is 2.5 mm, the light quantity is 40, the average filter is 2, The noise filter was set to 1.
The test piece was prepared by cutting a foam sheet having a width of 100 mm, a length of 100 mm, and a thickness (sheet thickness).
The number of test pieces was five, and the surface roughness in the extrusion direction and the flow direction of both front and back surfaces of each test piece was measured.
Arithmetic mean roughness (Ra) was obtained by adding the absolute values of deviations from the mean line to the measurement curve and averaging them with the reference length (n = 20).
The maximum height was determined from the sum of the height from the average line to the highest peak and the depth to the lowest valley (n = 20).
Moreover, the average length (Sm) of the contour curve element of the surface roughness is an arithmetic average value of the distance between the intersections of the average line and the contour line.

The polyester-based resin foam sheet has a bubble diameter of a certain size or more when considering that the fiber-reinforced composite exhibits light weight.
Therefore, if the bubble film on the sheet surface is simply depressed, the unevenness (surface roughness) on the sheet surface tends to be larger than the preferred range as described above.
In view of this, the polyester resin foam sheet temporarily sinks the cell membrane to make the surface roughness large, and then lifts a part of the individual cell membranes that are indented to the surface side (outside in the sheet thickness direction). Thus, it is preferable to adjust the surface roughness within the above preferred range.

Such an operation will be described below.
The said operation can be implemented in the flow of the following processes for producing a fiber reinforced composite.

(A) Sheet production process First, a polyester resin composition containing a foaming agent is melt-kneaded in an extruder equipped with a circular die, and the melt-kneaded product is extruded into a cylindrical shape from the annular discharge port of the circular die. The melt-kneaded product is foamed to form a cylindrical foamed sheet, and this cylindrical foamed sheet is continuously cut at one place or a plurality of places in the circumferential direction while being drawn downstream in the extrusion direction by a take-up machine. And a sheet production process for producing a long band-like foam sheet.
(B) Curing process Curing process in which the foamed sheet obtained in the sheet preparation process is stored at a predetermined temperature for a predetermined period, and the foaming agent remaining inside is replaced with external air and the strain generated during extrusion foaming is reduced. .
(C) Sheet smoothing process The sheet smoothing process which heats and pressurizes the foam sheet after the said curing process by hot press etc., and smoothes the surface rather than before a press.
(D) Preliminary body production process Preliminary body production process in which a fiber-reinforced resin sheet is temporarily bonded to the surface of a foam sheet that has been externally processed to a predetermined size to produce a preform.
(E) Lamination process The preform is placed in a mold having a cavity space corresponding to the product shape, and this is heated and pressed by a hot press or an autoclave to laminate a core material made of a foam sheet and a fiber reinforced resin sheet. A lamination process for producing a fiber reinforced composite in which a fiber reinforced resin layer is formed on the surface of a core material.

  Below, each process is demonstrated.

(A) Sheet preparation process The process includes, for example, melt-kneading a polyester-based resin composition containing a foaming agent in an extruder equipped with a circular die, and discharging the melt-kneaded material from an annular discharge port of the circular die. Extrude into a cylindrical shape, foam the melt-kneaded product to temporarily produce a cylindrical foamed sheet, and then pull this cylindrical foamed sheet downstream in the extrusion direction with a take-up machine, or one place in the circumferential direction, or multiple places Can be carried out by a method of cutting continuously into a long strip.
And the foam sheet which the bubble film which forms the sheet | seat surface indented in the sheet | seat thickness direction inner side by the setting of the conditions in this extrusion foaming can be produced.

This point will be described with reference to FIG.
FIG. 3 schematically shows the state of the cross section near the surface of the foam sheet indicated by the circle “X” in FIG. 2 and shows the state of bubbles near the surface in a microscopic form. It is.
In FIG. 3, the portion of the bubble film that defines the bubble Ac is formed with the symbol “A1a” indicating the portion forming the surface of the foam sheet, which is a partition wall between adjacent bubbles. The bubble film is denoted by the symbol “Alb”.

The method of forming irregularities on the sheet surface according to this figure will be described. First, as shown in FIG. 3 (a), the foam sheet immediately after extrusion is a bubble film constituting the surface under general production conditions. Is slightly overhanging outward in the sheet thickness direction.
In the present embodiment, by strongly cooling the surface of the foam sheet, the internal pressure of the bubbles Ac constituting the surface is reduced, and the bubble film A1a protruding outside is drawn into the bubbles.
As a result, as shown in FIG. 3 (b), the bubble film once bulged outward can be pulled back into the bubble, and the bubble Ac ′ on the surface of the sheet causes a depression Da of the bubble film A1a ′. Can be made.

Here, the depression depth of the bubble film is affected by the average bubble diameter in the sheet thickness direction (VD) of the bubbles constituting the sheet surface.
Moreover, in the extrusion direction (MD) and width direction (TD) of a foam sheet, it becomes a form where a depression part is formed in the form corresponding to the pitch of the bubble which comprises the sheet | seat surface.
That is, assuming that the average bubble diameter in MD is 10 μm, the formation pitch of depressions in MD is usually 10 μm on average.
Therefore, the unevenness of the sheet surface due to the depression of the bubble film can be adjusted by the average bubble diameter of the foam sheet.

The depth of depression of the bubble film can also be adjusted by the expansion property of the bubbles during extrusion foaming and the state of the bubble film on the surface when cooling is performed.
Specifically, when the bubble film is expanded to some extent at the start of cooling, the bubble film becomes thinner, so a large depression is likely to occur, and when the bubble film has a low melt tension, the bubble film has a larger depression. This is advantageous for formation.
Therefore, in order to cause a large depression, the following conditions are usually adopted at the time of extrusion foaming.

(1) Increasing the amount of foaming agent used to increase the expansibility of bubbles.
(2) The temperature setting of the circular die is increased to lower the melt tension of the bubble film on the sheet surface.
(3) The shear rate at the die lip is increased to reduce the thickness of the bubble film on the sheet surface.
(4) The diameter of the cylindrical foam sheet is increased after extrusion, and the cell membrane on the sheet surface is thinned by stretching.

  Further, in order to suppress the expansion of the bubble film on the sheet surface immediately after extrusion and the subsequent depression, it is only necessary to set conditions opposite to those described above.

By forming appropriate irregularities on the sheet surface in this way, the foamed sheet exhibits excellent adhesiveness with the fiber reinforced resin layer A1 due to the anchor effect.
However, in order to produce a foam sheet having the preferred surface roughness (Ra) as described above, it is necessary to set the above conditions with high accuracy.
Therefore, in this sheet manufacturing process, a foam sheet having a surface roughness rougher than the preferable surface roughness shown above may be manufactured, and the surface roughness may be adjusted by a subsequent sheet smoothing process.

(B) Curing Step The foamed sheet obtained in the sheet preparation step usually contains a foaming agent (hydrocarbon) in an amount exceeding the saturation solubility.
The extra foaming agent contained in the foamed sheet diffuses from the surface of the foamed sheet over time and is replaced with ambient air.
At this time, there is a possibility that the depressed state of the bubble film on the surface of the sheet may change slightly due to the replacement of the foaming agent and air.
In addition, the collapsed state of the bubble film on the surface of the sheet may change due to the strain relaxation of the foam sheet.
Therefore, it is preferable to provide a curing process and sufficiently stabilize the state of the foamed sheet before performing the sheet smoothing process.
This curing process can usually be performed by storing the foamed sheet in a state heated to a predetermined temperature for a predetermined period.

(C) Sheet smoothing step The sheet smoothing step of lifting a part of the foam film of the foam sheet in which the foam film is in a depressed state to reduce the surface unevenness is performed by the surface of the foam sheet near the glass transition point of the polyester resin. Can be carried out by heating to a temperature of
Specifically, the smoothing step is preferably performed by a method of hot pressing a foam sheet.
The sheet smoothing process by this hot press will be described with reference to FIG.
The bubble film A1a 'on the sheet surface in the depressed state is located in the bubble central part a2 away from the bubble film A1b' at the bubble peripheral part a1 near the bubble film A1b 'that exists as a partition wall between adjacent bubbles. In comparison, the film thickness is relatively thick.
That is, the bubble film A1a ′ in the depressed state has a smaller thickness than the peripheral edge at the center in the planar direction of each bubble Ac ′.
Therefore, when the surface of such a foam sheet is heated by bringing a hot plate HP of a hot press into contact with the surface, the thermal expansion of air in the bubbles and the bubbles of the foaming agent dissolved in the bubble film are introduced. As a result, the internal pressure of the bubble Ac ′ increases, and the central portion where the bubble film is thin is preferentially lifted as shown in FIG.
And in the peripheral part of each bubble, the bubble which comprises the sheet | seat surface will be in the folded state, and a micro unevenness | corrugation will be formed compared with the foam sheet before the said sheet | seat smoothing process is implemented. .
Here, the bubble film lifted to the outside in the sheet thickness direction is prevented from further outwardly protruding by contact with the hot plate HP, and the unevenness of the surface of the foam sheet is not only refined but also the sheet surface The flatness is also improved.
Therefore, the foamed sheet after the sheet smoothing step has a remarkable effect of suppressing the disturbance of the fibers of the base sheet upon lamination with the fiber reinforced resin sheet.
That is, from the viewpoint of reducing the unevenness of the surface of the foam sheet as compared with that before the smoothing step, the sheet smoothing step may be performed by non-contact heating with a far-infrared heater or the like. Contact heating such as rolls gives better results in the formation of fiber reinforced composites.

In addition, about (d) preforming body preparation process and (e) lamination process, it can carry out similarly to the method of conventional implementation.
In the laminating step, the resin of the fiber reinforced resin sheet can be impregnated into the fine depressions formed by the sheet smoothing step, and has excellent adhesion between the core material A1 and the fiber reinforced resin layer A2. A fiber reinforced composite A can be obtained.

As long as the foamed sheet is a polyester resin foamed sheet, the thickness and the apparent density are not particularly limited. Usually, a foamed sheet having a thickness of 0.5 to 5 mm can be adopted, and the apparent density is 0. A material of 0.01 to 0.7 g / cm ³ can be employed as the core material.

As the polyester-based resin that is a main raw material of the foamed sheet, for example, a high molecular weight linear polyester obtained as a result of a condensation reaction between a dicarboxylic acid and a polyhydric alcohol can be employed.
Examples of the polyester resin include aliphatic polyester resins such as aromatic polyester resins and polylactic acid resins.

The aromatic polyester resin is usually a polyester containing an aromatic dicarboxylic acid component and a diol component, for example, polyethylene terephthalate resin, polypropylene terephthalate resin, polybutylene terephthalate resin, polycyclohexanedimethylene terephthalate resin, polyethylene naphthalate resin, Examples include polybutylene naphthalate resin.
The aromatic polyester resin contained in the foamed sheet is preferably a polyethylene terephthalate resin.
In addition, an aromatic polyester resin may be used independently or 2 or more types may be used together.

  In addition to the aromatic dicarboxylic acid component and the diol component, the aromatic polyester resin includes, for example, a tricarboxylic acid such as trimellitic acid such as trimellitic acid, a tetracarboxylic acid such as pyromellitic acid, or a polyvalent carboxylic acid such as tricarboxylic acid or its anhydride. Products, triols such as glycerin, and trihydric or higher polyhydric alcohols such as tetraols such as pentaerythritol may be contained as constituent components.

  The aromatic polyester resin to be contained in the foamed sheet may be a recycled material collected and regenerated from a used plastic bottle.

The aromatic polyester resin contained in the foamed sheet may be partially crosslinked as long as it is within the range where thermoplasticity is exhibited.
Examples of the crosslinking agent for crosslinking an aromatic polyester resin such as polyethylene terephthalate resin include acid dianhydrides such as pyromellitic anhydride, polyfunctional epoxy compounds, oxazoline compounds, and oxazine compounds.
In addition, a crosslinking agent may be used independently or 2 or more types may be used together.

When the polyethylene terephthalate resin is crosslinked with a crosslinking agent, the crosslinking agent may be supplied together with the polyethylene terephthalate resin to the extruder and dynamically crosslinked in the extruder.
If the amount of the crosslinking agent supplied to the extruder is too small, the melt viscosity of the polyethylene terephthalate resin may be insufficient.
That is, if the amount of the cross-linking agent is too small, the melt viscosity of the polyethylene terephthalate resin after cross-linking is too low, and foam breakage may easily occur when the foamed sheet is extruded and foamed.
On the other hand, if the amount of the crosslinking agent is too large, the melt viscosity of the polyethylene terephthalate resin becomes too high, and when the foamed sheet is produced by extrusion foaming, the load on the extruder becomes too high and the extrusion foaming itself is difficult. There is a risk.
Therefore, when the base resin of the resin composition for constituting the core material is a cross-linked polyethylene terephthalate resin, a cross-linking agent is used at a ratio of 0.01 to 5 parts by mass with respect to 100 parts by mass of the polyethylene terephthalate resin. It is preferable to employ a crosslinked one.
The ratio is more preferably 0.1 to 1 part by mass.

As the polylactic acid resin, a resin in which lactic acid is polymerized by an ester bond can be used.
When the thermoplastic resin contained in the foam sheet is a polylactic acid resin, from the viewpoint of commercial availability and ease of imparting foamability, the polylactic acid resin is D-lactic acid (D form) and L -Copolymer of lactic acid (L-form), homopolymer of either D-lactic acid or L-lactic acid, one or two or more selected from the group consisting of D-lactide, L-lactide and DL-lactide Lactide ring-opening polymers are preferred.
In addition, polylactic acid-type resin may be used independently, or 2 or more types may be used together.

The polylactic acid-based resin may contain an aliphatic polyhydric alcohol or the like as a monomer component other than lactic acid.
Examples of the monomer component include aliphatic hydroxycarboxylic acids such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, and hydroxyheptanoic acid; succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedicarboxylic acid. Aliphatic polycarboxylic acids such as succinic anhydride, adipic anhydride, trimesic acid, propanetricarboxylic acid, pyromellitic acid, pyromellitic anhydride; ethylene glycol, 1,4-butanediol, 1,6-hexanediol, Examples include 1,4-cyclohexanedimethanol, neopentyl glycol, decamethylene glycol, glycerin, trimethylolpropane, and pentaerythritol.

The polylactic acid-based resin may have a functional group such as an alkyl group, a vinyl group, a carbonyl group, an aromatic group, an ester group, an ether group, an aldehyde group, an amino group, a nitrile group, or a nitro group.
The polylactic acid-based resin may be crosslinked with an isocyanate-based crosslinking agent or the like, and may have a bond other than an ester bond in the main chain or side chain.

  The foamed sheet is prepared by appropriately blending such a base resin with a foaming agent or a cell nucleating agent to prepare a polyester resin composition suitable for extrusion foaming, and this is an extrusion equipped with a circular die or flat die. It can be produced by extrusion foaming with a machine.

  As the foaming agent, a chemical foaming agent or a physical foaming agent can be appropriately employed.

Examples of the chemical foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, hydrazoyl dicarbonamide, sodium bicarbonate, and the like.
In addition, a chemical foaming agent may be used independently or 2 or more types may be used together.

Examples of the physical blowing agent include saturated aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane and hexane, ethers such as dimethyl ether, methyl chloride, 1,1,1,2-tetrafluoroethane. Chlorofluorocarbons such as 1,1-difluoroethane and monochlorodifluoromethane, carbon dioxide, nitrogen and the like, dimethyl ether, propane, normal butane, isobutane and carbon dioxide are preferable, propane, normal butane and isobutane are more preferable, normal butane, Isobutane is particularly preferred.
In addition, a physical foaming agent may be used independently or 2 or more types may be used together.

  Moreover, you may use together a chemical foaming agent and a physical foaming agent.

  Examples of the cell nucleating agent include talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, and sulfuric acid. Examples include inorganic compound particles such as potassium, barium sulfate, and glass beads, and organic compound particles such as polytetrafluoroethylene.

  In addition, the polyester-based resin composition for producing a foam sheet includes an antioxidant, an antioxidant, a weathering agent, an antibacterial agent, a flame retardant, an antistatic agent, an antifungal agent, a fungicide, a pigment, Various additives such as can be contained.

  On the other hand, the fiber-reinforced resin sheet may be of a type having a base sheet such as a fiber woven fabric or a non-woven fabric, or of a type in which a mixture of a resin and a short fiber is formed into a sheet. .

The fibers and short fibers constituting the base sheet of the fiber reinforced resin sheet are, for example, metal fibers such as stainless fibers and steel fibers, glass fibers, carbon fibers, boron fibers, silicon carbide fibers, alumina fibers, Tyranno fibers, and basalt fibers. And other inorganic fibers such as ceramic fibers; organic fibers such as aramid fibers, polyethylene fibers, and polyparaphenylene benzoxador (PBO) fibers;
Among them, the fibers constituting the fiber reinforced resin sheet are preferably carbon fibers, glass fibers, and aramid fibers, and more preferably carbon fibers because they have excellent mechanical strength and heat resistance.

  As the base material sheet, for example, a face material obtained by plain weaving, twill weaving, or satin weaving of aligned yarns or twisted yarns obtained by arranging a plurality of the fibers can be employed.

The base sheet may be composed of only one face material, or a plurality of face materials may be laminated.
Also, the fiber reinforced resin layer need not be composed of only one fiber reinforced resin sheet, and the fiber reinforced resin layer can be formed of a plurality of fiber reinforced resin sheets.

  In addition, about the said short fiber, a thing whose thickness is 3 micrometers or more and 20 micrometers or less normally, and whose length is 3 mm or more and 50 mm or less is employable.

Resin utilized for formation of a fiber reinforced resin sheet with the said base material sheet and the said short fiber is not specifically limited, A general thermoplastic resin and a thermosetting resin are mentioned.
The thermoplastic resin is not particularly limited, and examples thereof include olefin resins, polyester resins, polyamide resins, thermoplastic polyurethane resins, sulfide resins, and acrylic resins.
In addition, a thermoplastic resin may be used independently or 2 or more types may be used together.
The resin constituting the fiber reinforced resin sheet is preferably a polyester resin among thermoplastic resins in consideration of adhesiveness with the foamed sheet.

The thermosetting resin constituting the fiber reinforced resin sheet is not particularly limited. For example, epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, polyurethane resin, silicon resin, maleimide resin, vinyl ester resin, cyanide. Examples include acid ester resins, resins obtained by prepolymerizing maleimide resins and cyanate ester resins, and epoxy resins and vinyl ester resins are preferred because of excellent heat resistance, elastic modulus, and chemical resistance.
In addition, a thermosetting resin may be used independently or 2 or more types may be used together.

The resin content in the fiber reinforced resin sheet is preferably 20 to 70% by mass, and more preferably 30 to 60% by mass.
Moreover, 0.02-2 mm is preferable and, as for the thickness of a fiber reinforced resin sheet, 0.05-1 mm is more preferable.

In addition, in this embodiment, although the above illustrations are performed about the polyester-type resin foam sheet, its manufacturing method, and a fiber reinforced composite, this invention is not limited to the said illustration.
In addition, the polyester resin foam sheet in which the bubble film on the surface is depressed to form irregularities on the surface is not limited to the above-described usage method, for example, when extruding and laminating a resin film. It can be expected that an excellent anchor effect is exhibited.
In addition, the polyester resin foam sheet of the present invention can also utilize a portion where the bubble film is depressed as a non-adhesive region when the resin film is heat laminated.
That is, the polyester-based resin foam sheet of the present invention is useful even in the case where the adhesion area with the resin film is appropriately reduced by reducing the adhesion area.
In addition, the polyester resin foam sheet can use a minute concave portion formed on the surface by sinking the cell membrane as a space for holding a functional drug or the like.
That is, a functional agent such as a fragrance or a biological repellent may be accommodated in the minute recesses so that the polyester resin foam sheet exhibits a specific function.
In that case, a polyester resin nonwoven fabric sheet is laminated on the polyester resin foam sheet containing the functional drug in the minute recesses, and the release of the functional drug is imparted to the polyester resin foam sheet. It may be.
As described above, the polyester resin foam sheet of the present invention can exhibit an excellent function not only when used as a core material of a fiber-reinforced composite but also in various applications.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.
(Examples 1-2)
100 parts by weight of polyethylene terephthalate (PET, trade name “SA135” manufactured by Mitsui Chemicals, glass transition temperature Tg: 79 ° C., melting point: 247.1 ° C., IV value: 0.86), 0.72 parts by weight of talc, and A thermoplastic polyester resin composition containing 0.2 parts by weight of pyromellitic anhydride was supplied to a single screw extruder having a diameter of 65 mm and an L / D ratio of 35, and melt kneaded at 290 ° C.

  Next, from the middle of the single-screw extruder, a thermoplastic polyester resin in a molten state so that butane containing 35% by weight of isobutane and 65% by weight of normal butane is 1.0 part by weight with respect to 100 parts by weight of polyethylene terephthalate. The composition was pressed into the composition and uniformly dispersed in the thermoplastic polyester resin composition.

Then, after the thermoplastic polyester resin composition in a molten state is cooled to 220 ° C. at the front end of the single screw extruder, it is extruded and foamed into a cylindrical shape from a circular die attached to the front end of the single screw extruder. After the cylindrical body is gradually expanded in diameter and supplied to a cooling mandrel to cool the cylindrical body so that its surface temperature is 25 ° C., the cylindrical body is moved in the extrusion direction. A polyethylene terephthalate foam sheet having a thickness of 3.2 mm and a weight per unit area of 900 g / cm ³ was manufactured by continuously cutting between the inner and outer peripheral surfaces and opening and developing.
The cooling mandrel contact surface was the front surface, and the opposite surface was the back surface. Immediately after production, the foam sheet was cured at room temperature of 25 ° C. for 48 hours.

(Examples 3 to 4)
From the middle of the single-screw extruder, a thermoplastic polyester resin composition in a molten state so that butane containing 35% by weight of isobutane and 65% by weight of normal butane is 0.5 parts by weight with respect to 100 parts by weight of polyethylene terephthalate. A foamed sheet was obtained in the same manner as in Examples 1 and 2 except that a polyethylene terephthalate foamed sheet having a thickness of 2.0 mm and a basis weight of 600 g / cm ³ was produced by press-fitting.

(Examples 5-6)
From the middle of the single screw extruder, a molten polyester resin composition containing 0.3% by weight of butane containing 35% by weight of isobutane and 65% by weight of normal butane is added to 100 parts by weight of polyethylene terephthalate. A foamed sheet was obtained in the same manner as in Examples 1 and 2, except that a polyethylene terephthalate foamed sheet having a thickness of 1.7 mm and a basis weight of 500 g / cm ³ was produced.

(Examples 7 to 8)
A foam sheet was prepared in the same manner as in Examples 1 and 2, and a sheet smoothing step was performed.
That is, a flat square sheet piece having a side of 640 mm was cut out from the foam sheet.
The cut sheet piece was laid in a press machine provided with a 3.0 mm spacer, and pressed at a temperature of 140 ° C. and a pressure of 0.5 MPa for 3 minutes.
Then, it cooled to 30 degreeC, hold | maintaining a pressure, and obtained the foam sheet (sheet piece) by which the thickness of Table 1 and the surface weight of surface weight were smooth | blunted.

(Examples 9 to 10)
A foam sheet was prepared in the same manner as in Examples 5 to 6, and a sheet smoothing step was performed.
A flat square sheet piece having a side of 640 mm was cut out from the foam sheet.
The cut sheet piece was laid in a press machine provided with a 3.0 mm spacer, and pressed at a temperature of 140 ° C. and a pressure of 0.5 MPa for 3 minutes.
Then, it cooled to 30 degreeC with the pressure hold | maintained, and obtained the foam sheet with which the thickness of Table 1 and the fabric weight of the fabric weight were smooth | blunted.

In addition, the photograph (surface photograph) which microscopically observed the surface state of the foam sheet of Example 2 and the surface state of the foam sheet of Example 8 after implementing a sheet | seat smoothing process to the same foam sheet is shown in FIG. .
In Example 2 (FIG. 5 (X)) before the sheet smoothing step, bubbles which are depressed only in a small region as indicated by an arrow D are scattered, but are generally seen by arrows A to C. As can be seen, the entire area of the bubble was greatly depressed.
On the other hand, in Example 8 (FIG. 5 (Y)) before the sheet smoothing step, as shown by the arrows A to D, each bubble remains a depressed structure in a state of an elongated groove, and the others. The area was flattened, and the state of the depression was refined.
Moreover, in Example 8, as shown by the arrow a, there were some cases in which two bubbles were formed in one bubble.

This also shows that according to this invention, the fiber reinforced composite excellent in the adhesive strength of a fiber reinforced resin layer and a core material can be provided.
Further, it can be seen that it is particularly effective to perform the sheet smoothing step in order to exert such an effect.

Claims (3)

A polyester-based resin foam sheet used as a core material of a fiber-reinforced composite,
A polyester-based resin foam sheet in which a cell membrane forming the sheet surface is depressed inward in the sheet thickness direction to form irregularities on the sheet surface. A method for producing a polyester resin foam sheet in which a sheet production step of producing a polyester resin foam sheet by extrusion foaming a polyester resin composition containing a foaming agent is performed,
In the sheet manufacturing step, the surface of the polyester-based resin foam sheet is cooled to cause the bubble film on the sheet surface to sink inward in the sheet thickness direction, and the polyester-based resin foam sheet in which irregularities are formed on the sheet surface by the depression of the bubble film The manufacturing method of the polyester-type resin foam sheet which produces this.   Heating the surface of the polyester-based resin foam sheet in which the bubble film is depressed, lifting a portion of the depressed bubble film outward in the sheet thickness direction, and the polyester system in which the surface unevenness is made finer than before the heating The manufacturing method of the polyester-type resin foam sheet of Claim 2 which implements the sheet smoothing process which forms a resin foam sheet after the said sheet preparation process.