JP7123964B2 - thermoplastic fiber sheet - Google Patents

Description

The present invention relates to thermoplastic fiber sheets.

A wire harness is a collective component made by bundling a plurality of electric wires used for power supply and signal communication. It is used in a variety of mechanical devices that require a large amount of electrical wiring, such as in-vehicle wiring in automobiles.

Here, a plurality of electric wires forming the wire harness are bundled with a protector. As one method for bundling the electric wires, a method has been proposed in which a plurality of electric wires are wound with a non-woven fabric and heat-molded. Here, as the nonwoven fabric, for example, Patent Document 1 proposes a nonwoven fabric composed of a basic resin that is a thermoplastic resin fiber and an adhesive resin having a melting point lower than that of the basic resin.

JP 2012-196035 A

In the method of manufacturing a wire harness using the nonwoven fabric according to Patent Document 1, first, a step of winding a plurality of wires with the nonwoven fabric (temporary fixing step) is performed, and then the nonwoven fabric wrapped around the plurality of wires is heated and melted. A step (main fixing step) is carried out.

Here, during this temporary fixing step, the ends of the wrapped nonwoven fabric may float due to its rigidity. In this case, a phenomenon occurs in which the wound nonwoven fabric is unraveled. Furthermore, if the end portion is heated and melted in a floating state, the end portion is permanently fixed in the floating state, and it is necessary to remove the floating portion of the end portion. Therefore, in order to prevent these problems, it is necessary to heat and melt while firmly fixing the end portion so that the end portion does not float, which is troublesome.

Therefore, the present invention provides a thermoplastic fiber sheet suitable for use in which an object (e.g., a plurality of electric wires) is coated (e.g., wound) and then heated and melted to attach (e.g., fix) to the object, It is an object of the present invention to provide a means for temporarily fixing before heating and fusing, by which the ends of a thermoplastic fiber sheet can be simply fixed, or need not be fixed.

The present inventors have found that the above problems can be solved by combining thermoplastic resin fibers and cellulosic fibers to form a sheet, and further by forming a sheet so that the WET strength is within a predetermined range. Inventions (1) to (5) were completed.

The present invention (1) comprises at least cellulosic fibers and thermoplastic resin fibers, and the weight ratio of the cellulosic fibers to the thermoplastic resin fibers (the cellulosic fibers: the thermoplastic resin fibers) is The thermoplastic fiber sheet has a ratio of 6.5:3.5 to 2:8 and a WET strength of 7 N/cm or more and less than 20 N/cm.

The present invention (2) is the thermoplastic fiber sheet according to the invention (1), wherein the thermoplastic fiber sheet has a water retention rate of 50 to 220%.

Invention (3) is the thermoplastic fiber sheet according to invention (1) or (2), wherein the thermoplastic resin fibers are main fibers made of one or more thermoplastic resins.

In the present invention (4), the thermoplastic fiber sheet is attached to the object by temporarily fixing the thermoplastic fiber sheet to the object and then thermally fusing the thermoplastic resin fibers. The thermoplastic fiber sheet according to any one of the inventions (1) to (3), which is used for permanent fixation.

Here, the thermoplastic fiber sheet may be used in an application in which the temporary fixing is performed in a state in which the thermoplastic fiber sheet contains a liquid (a state in which the thermoplastic fiber sheet is impregnated with a liquid). Furthermore, in this case, the thermoplastic fiber sheet is subjected to a high temperature treatment (high temperature It may be used in applications where it is removed by exposing to the bottom).

The present invention (5) is the thermoplastic fiber sheet according to any one of the above inventions (1) to (4), which is used as a wire harness protector.

According to the present invention, a thermoplastic fiber sheet suitable for use in which an object (e.g., a plurality of electric wires) is covered (e.g., wound) and then heated and melted to attach (e.g., fix) to the object, It is possible to provide a means for temporarily fixing the thermoplastic fiber sheet before heating and fusing, by simply fixing the ends of the thermoplastic fiber sheet or by eliminating the need for fixing.

Here, the reason why the thermoplastic fiber sheet according to the present invention exhibits the above effects is not necessarily clear, but is presumed to be as follows. In the following description, the case of using water as the liquid to be described later will be taken as an example.

First, when the thermoplastic fiber sheet according to the present invention is wound in a water-adhered state, the cellulosic fiber and the thermoplastic resin fiber are in a predetermined ratio, and the WET strength is in a predetermined range ( In other words, as a result of the structure to be described later), when processed into an arbitrary shape, it becomes flexible and easy to move, and stiffness is reduced. The reason for this is considered as follows.

First, by being immersed in water under the above configuration, the hydrogen bonds between the cellulosic fibers are moderately broken, and the binding force between the cellulosic fibers is moderately weakened. Further, the moderate swelling makes the sheet moderately sparse. For these reasons, the thermoplastic fiber sheet is understood to be moderately flexible and easy to move, and moderately low in stiffness.

Next, after processing into an arbitrary shape, the arbitrary shape is maintained by drying to remove water. The reason for this is considered as follows.

First, by setting the cellulosic fiber and the thermoplastic resin fiber to a predetermined ratio and setting the WET strength to a predetermined range (in other words, as a result of the structure described later), swelling occurred in the process of losing moisture. The cellulosic fibers gradually become denser. Then, while the thermoplastic resin fibers are kept in a moderately bent shape, the cellulosic fibers are appropriately entangled, and hydrogen bonds are formed between the cellulosic fibers. For this reason, it is understood that the thermoplastic fiber sheet can be fixed while being bent into any shape.

<<<thermoplastic fiber sheet>>>
The thermoplastic fiber sheet according to the present invention comprises at least cellulosic fibers and thermoplastic resin fibers, and the weight ratio of the cellulosic fibers to the thermoplastic resin fibers (the cellulosic fibers: the thermoplastic resin fiber) is 6.5:3.5 to 2:8, and the WET strength is 7 N/cm or more and less than 20 N/cm.

The sheet may have a single-layer structure or a multi-layer structure. However, as described below, the single-layer structure is preferable because it is easier to secure uniformity in the thickness cross-sectional direction of the thermoplastic fiber sheet and entanglement between fibers.

Here, the "layer" in "single layer" and "multilayer" means a structural unit in which the fiber composition in the layer is substantially the same. In the case of a single layer, the layer should contain at least cellulosic fibers and thermoplastic resin fibers, and in the case of multiple layers, any layer may contain cellulosic fibers and thermoplastic resin fibers, respectively. Good luck. In the case of multiple layers, it is preferable to include at least one layer in which the weight ratio of the cellulose fiber and the thermoplastic resin fiber satisfies the specific range of the present invention (in this case, what kind of layer is the other layer? may be used).

Hereinafter, each element constituting the thermoplastic fiber sheet according to the present invention, the composition of each element of the thermoplastic fiber sheet according to the present invention, and the properties of the thermoplastic fiber sheet according to the present invention will be described in order.

<<Elements of Thermoplastic Fiber Sheet>>
<Cellulose fiber>
Cellulosic fibers of the thermoplastic fiber sheet according to the present invention are not particularly limited. mechanical pulps such as pressure-rised groundwood pulp (PGW) and thermomechanical pulp (TMP);

In addition, cellulosic fibers include wood pulp made from materials such as N and L; cotton, straw, bamboo, esparto, kenaf, cotton, bagasse, flax, hemp, jute, non-wood pulp made from ganpi or the like;

Here, specific examples of kraft pulp include softwood high yield unbleached kraft pulp (HNKP; N material), softwood bleached kraft pulp (NBKP; N material, NB material), hardwood unbleached kraft pulp (LUKP; L material). , hardwood bleached kraft pulp (LBKP; L material), and the like.

The cellulosic fiber may be waste paper pulp such as deinking pulp (DIP) and waste pulp (WP).

These cellulosic fibers may be used singly or in combination of two or more.

As the cellulosic fiber, among these, NBKP, hemp, and Manila hemp pulp are preferable, and NBKP is particularly preferable. When these are used as cellulosic fibers, for unknown reasons, they have good compatibility with thermoplastic resins (in particular, they are remarkably good in combination with resin fibers that are preferred in the present specification), and in wet conditions A thermoplastic fiber sheet having high tensile strength can be obtained.

The cellulosic fiber preferably has a freeness of 200 to 700 ml. The freeness of cellulosic fibers means the value of Canadian Standard Freeness (CSF), JIS P 8121-2: 2012 "Pulp-Freeness Test Method-Part 2: Canadian Standard Freeness Method". can be measured according to

<Thermoplastic resin fiber>
The thermoplastic resin fibers of the thermoplastic fiber sheet according to the present invention are not particularly limited as long as they are fibers made of thermoplastic resin.

Specific examples of thermoplastic resins include amorphous polyester, amorphous polyolefin, copolyester, high-density polyethylene, polypropylene, acrylonitrile styrene, ABS, polyvinyl chloride, PMMA, polycarbonate, and ethyl cellulose. .

These thermoplastic resins may be used singly or in combination of two or more.

From the viewpoint that permanent fixation can be performed even at a low heating temperature, the softening temperature of the thermoplastic resin is preferably 100° C. or higher and 140° C. or lower (a more preferable lower limit is 110° C., and a more preferable upper limit is 130° C.). is.

Here, the softening temperature can be measured by using a thermomechanical analyzer (TMA).

(Method for measuring softening temperature)
The softening temperature of thermoplastic resin fibers can be measured, for example, by the following method. An arbitrary amount of thermoplastic resin fibers is sandwiched between metal plates made of SUS304 with a thickness of 1 mm and a size of 100 × 150 mm, and pressed for 60 minutes at a press temperature of 100 ° C. and a press pressure of 0.1 MPa. A molded block is prepared, and a portion free of air bubbles is selected from the molded block by observation with transmitted light. The softening temperature is measured using a TMA SS6100 manufactured by Hitachi High-Tech Science as a TMA measuring device with a 1 mm diameter quartz glass needle probe under the conditions of a heating rate of 5° C./min and a load of 30 mN.

Here, the thermoplastic resin fibers are preferably main fibers. The term "main fiber" refers to a fiber having substantially a single composition in cross section, and for example, a fiber having a non-core-sheath structure (a fiber having no core-sheath structure). In more detail, the substantially single composition fiber can also be interpreted as a fiber having a substantially uniform composition distribution in the cross section of the fiber (substantially uniform composition fiber). In addition, the components constituting the substantially single composition may consist of one kind of thermoplastic resin as described above, or may consist of two or more kinds of thermoplastic resins. The reasons why main fibers are suitable are described below.

For example, since fibers having a core-sheath structure have a core, they tend to generate resistance against bending stress. That is, when subjected to bending stress, strain is likely to accumulate at the interface between the core and the sheath, so it is presumed that a force tending to return to the original shape against bending is likely to act. A main fiber that does not have such characteristics does not easily interfere with the temporary fixability.

In addition, it is necessary to heat and melt in the final fixing step. In an actual manufacturing process, it is desirable to be able to process at the lowest possible temperature and in the shortest possible time in order to reduce thermal damage to the wire harness, for example, assuming the use of the wire harness.

At this time, by using the main fibers, the melting temperature of the outer peripheral portion and the melting temperature of the central portion become the same, and in the main fixing step, it is not necessary to set the temperature according to the melting temperature of the outer peripheral portion. If the melting temperature of the central portion is higher than that of the outer peripheral portion, the rigidity of the resin fiber as a whole increases during heating, which may lead to a decrease in fixing force. Conversely, if the melting temperature of the central portion is lower than that of the outer peripheral portion, only the inner portion will melt first in the main fixing step, making it difficult to maintain the shape of the fiber, which may lead to a decrease in mechanical strength.

As described above, when the main fiber is used, the effects of the present invention can be enhanced more than when the core-sheath structure fiber is used.

The fineness of the thermoplastic resin fibers is preferably 1-10 dtex, more preferably 2-6 dtex. When the fineness of the thermoplastic resin fiber is within the range, the effects of the present invention can be enhanced.

The fiber length of the thermoplastic resin fibers is preferably 1-10 mm, more preferably 4-6 mm. When the fineness of the thermoplastic resin fiber is within the range, the effects of the present invention can be enhanced.

In particular, when the thermoplastic resin fiber is a copolymer polyester fiber having a fineness and/or a fiber length within the above range, the effects of the present invention can be further enhanced.

<Others>
The thermoplastic fiber sheet according to the present invention optionally contains other known ingredients such as dyes, drainage improvers, paper strength agents, thickeners, dispersants, antifoaming agents, fillers, and the like. may Further, these components may be present between the fibers of the thermoplastic fiber sheet, on the surface or inside the thermoplastic resin fibers, or on the surface or inside the cellulosic fibers.

However, it is preferable that the thermoplastic fiber sheet according to the present invention does not contain a paper strength agent and a sizing agent, or the content thereof is small. When the paper strength agent and sizing agent are not contained or the content is small, when a liquid (eg, water or ethanol) is added to the thermoplastic fiber sheet during temporary fixing, only the cellulosic fibers tend to become slurry-like. This is presumed to be one of the mechanisms of action that enhance the effects of the present invention.

<<Formulation of thermoplastic fiber sheet>>
In the present invention, the weight ratio of the cellulosic fibers and the thermoplastic resin fibers (the cellulosic fibers: the thermoplastic resin fibers) is 6.5:3.5 to 2:8, and 6:4. ∼2.5:7.5, more preferably 5:5 to 3:7. In addition to the WET strength described below being within the predetermined range, the weight ratio being within the above range makes it possible to achieve the effects of the present invention.

The thermoplastic fiber sheet preferably contains 80% by mass or more of cellulosic fibers and thermoplastic resin fibers based on the total mass of the thermoplastic fiber sheet, and preferably 90% by mass or more. It is more suitable.

In addition, it is preferable that the content of each of the paper strength agent and the sizing agent in the thermoplastic fiber sheet is 1% by mass or less based on the total mass of the thermoplastic fiber sheet.

<<Properties of thermoplastic fiber sheet>>

<Wet strength>
The WET strength of the thermoplastic fiber sheet according to the present invention is 7 N/cm or more and less than 20 N/cm, preferably 8 N/cm or more and 18 N/cm or less, and 10 N/cm or more and 17 N/cm or less. It is more suitable. When the WET strength is within the above range, it is possible to secure the tensile strength actually necessary for temporary fixing, and to maintain the swelling and deformation effects of the cellulosic fibers.

(WET intensity measurement method)
Here, the WET intensity is a value measured by the following method. Each measurement method including this method was carried out at 25° C. under atmospheric pressure unless otherwise specified.

First, a thermoplastic fiber sheet (sample) is cut into 10 mm×200 mm. The sample is immersed in tap water (temperature: 20°C, time: 10 seconds). The soaked sample is then wiped with dry Bemcot to remove excess water. Thereafter, the tensile strength is measured using a Tensilon manufactured by Orientec in accordance with JIS P8113 {test conditions: test length is 180 mm (each end is chucked about 10 mm), test speed is 30 mm/min}. The test is performed 3 times (N=3) for each sample and the average value is taken.

<Adhesion strength>
The adhesive strength of the thermoplastic fiber sheet according to the present invention is preferably 1.2N or more, more preferably 1.5N or more.

(Method for measuring adhesive strength)
Here, the adhesive strength is a value measured by the following method.

First, a thermoplastic fiber sheet (sample) is cut into 100 mm×40 mm (2 sheets are prepared). These two samples are superimposed and pressure-bonded by a hot press. The hot press conditions are 100° C./0.5 MPa/10 seconds. After that, the tensile strength is measured using a Tensilon manufactured by Orientec in accordance with JIS K6854-3 {test conditions: measurement of T-shaped peel strength; test speed: 30 mm/min}. The test is performed 3 times (N=3) for each sample and the average value is taken.

<Water retention rate>
The water retention rate of the thermoplastic fiber sheet according to the present invention is preferably 50% or more, more preferably 70% or more, and even more preferably 80% or more. Also, the upper limit of the water retention rate is not particularly limited, but is, for example, 220%.

The water retention rate is an important factor that provides the thermoplastic fiber sheet of the present invention with the effect of reducing stiffness due to swelling. That is, when the water retention rate of the thermoplastic fiber sheet is in the range of 50% to 220%, the hydrogen bonds between the cellulosic fibers in the thermoplastic fiber sheet are moderately broken and the bonds between the cellulosic fibers are broken. Power tends to be moderately weak. Furthermore, moderate swelling tends to make the sheet moderately sparse. For these reasons, the thermoplastic fiber sheet is understood to be moderately flexible and easy to move, and moderately easy to reduce stiffness. It is presumed that the thermoplastic fiber sheet is then dried, thereby facilitating the development of a primary fixing effect that can withstand practical use.

(Method for measuring water retention rate)
Here, the water retention rate is a value measured by the following method.

First, a thermoplastic fiber sheet is cut into 50 mm×50 mm. After that, it is placed in a pressure container and left for 1 hour in a vacuum state using a rotary pump to completely dry the thermoplastic fiber sheet. After that, immediately after taking out the thermoplastic fiber sheet, the absolute dry weight is measured (three decimal places). The thermoplastic fiber sheet is then immersed in water (temperature: 20°C; time: 5 seconds). Excess moisture is then removed.

Specifically, a thermoplastic fiber sheet is sandwiched between dry BEMCOT, an aluminum plate of 5 cm square and 1 mm in thickness is placed directly above the thermoplastic fiber sheet, a weight of 500 g is placed on the aluminum plate and waited for 30 seconds. After that, only the thermoplastic fiber sheet that has absorbed water is taken out, and the weight is measured again 30 seconds after the weight is removed, and the weight after water retention (thermoplastic fiber sheet from which excess water has been removed) is taken.

Then, the water retention amount is calculated by subtracting the weight in the absolute dry state from the weight after water retention, and the water retention rate is calculated by dividing the water retention amount by the weight at the time of drying. The test is performed three times (N=3) for each thermoplastic fiber sheet, and the average value is adopted.

<<Method for producing thermoplastic fiber sheet>>
The method for producing the thermoplastic fiber sheet according to the present invention can generally be produced by a known papermaking method. For example, cellulose fibers, thermoplastic resin fibers, and, if necessary, other components are dispersed in water to prepare a raw material slurry, and the resulting raw material slurry is wet paper-made to obtain a thermoplastic fiber sheet.

Here, the cellulosic fibers are preferably beaten in advance. The beating can be appropriately carried out by a beating machine such as a single disc refiner (SDR), a double disc refiner (DDR) and a beater.

In addition, the wet paper machine used for wet papermaking is not particularly limited, and paper machines that are applied to general papermaking technology, specifically, Fourdrinier paper machine, cylinder paper machine, inclined paper machine, twin wire paper machine Machines, etc. can be used.

However, one feature of the thermoplastic fiber sheet according to the present invention is that it has a WET strength of 7 N/cm or more and less than 20 N/cm.

In order to set the WET strength to 7 N/cm or more and less than 20 N/cm, first, it should be noted that the cellulosic fibers/thermoplastic resin fibers should not be unevenly distributed in the cross-sectional direction of the thickness of the thermoplastic fiber sheet. is preferred. This is because if the cellulosic fibers/thermoplastic resin fibers are unevenly distributed, the mechanism of improving flexibility during immersion→swelling and fixing by entanglement of the pulp after drying does not work well.

Secondly, in order to make the WET strength to be 7 N/cm or more and less than 20 N/cm, it is preferable to appropriately entangle the cellulosic fibers/thermoplastic resin fibers. While it is important to swell by immersion, if the cellulosic fibers are too close to each other, the space becomes narrow, and as a result, the water retention amount (=swelling amount) during immersion is reduced. As a result, the flexibility is lowered, the cellulosic fibers are easily damaged during processing, and the temporary fixing ability after drying is lowered.

As described above, in order to set the WET strength to 7 N/cm or more and less than 20 N/cm, it is preferable to pay attention to the selection of materials and processes.

First, regarding the selection of materials, it is preferable to set the weight ratio of the cellulosic fiber to the thermoplastic resin fiber (said cellulosic fiber: said thermoplastic resin fiber) to 6.5:3.5 to 2:8. A WET strength of 7 N/cm or more and less than 20 N/cm can be achieved by setting such a weight ratio and performing the process described later.

The following points are preferable from the ordinary papermaking method.

First, in the slurry dispersing step, it is preferable to gradually add the cellulosic fibers to the slurry in which only the thermoplastic resin fibers are previously dispersed. If a predetermined amount of cellulosic fiber is added all at once, it is difficult to form an appropriate gap between the thermoplastic resin fiber and the cellulosic fiber, and the cellulosic fibers are too close to each other, resulting in unevenness of the sheet. This is because it is likely to damage the water retention capacity and may lead to a decrease in the water retention capacity.

Secondly, in the papermaking process, it is preferable to gently perform suction for dehydration. This is because the gradual dehydration makes it easier to prevent uneven distribution of cellulosic fibers and thermoplastic resin fibers particularly in the surface direction.

Thirdly, in the drying process after papermaking, the distance between fibers narrows due to evaporation of moisture contained between cellulosic fibers. Here, in the drying process after papermaking, the amount of water vapor in the air is dried while maintaining a higher concentration than in the normal papermaking method, that is, by drying gradually, the shrinkage of the gaps between the cellulose fibers is suppressed. It becomes easy to obtain a sheet with high quality.

Fourthly, it is preferable to use no or only a small amount of paper strength agents and sizing agents in order to maintain tensile strength and sufficient water retention in a wet state.

<<How to use the thermoplastic fiber sheet>>
The thermoplastic fiber sheet according to the present invention includes a step of attaching the thermoplastic fiber sheet to an object (temporary fixing: first fixing), before the attachment (that is, before temporary fixing), or after the attachment (that is, after temporary fixing). includes a step of attaching a liquid to the thermoplastic fiber sheet, a step of removing the liquid from the thermoplastic fiber sheet, and a step of heat-sealing the thermoplastic fiber sheet to the object (main fixing: second fixing). Each element is described below.

<Step of attaching thermoplastic fiber sheet to object: step of attaching thermoplastic fiber sheet>
First, the process of adhering the thermoplastic fiber sheet to the object will be described.

The object is not particularly limited, and may be, for example, an object having a curved surface (for example, a plurality of wires arranged side by side) or a planar object (for example, a wall). However, considering the problems with conventional thermoplastic fiber sheets, such as "lifting of the ends" and "unraveling" when the thermoplastic fiber sheet is temporarily fixed to an object having a curved surface, the thermoplastic fiber sheet according to the present invention Objects of the fiber sheet are particularly suitable for objects with curved surfaces.

<Step of Adhering Liquid to Thermoplastic Fiber Sheet: Liquid Adhering Step>
Next, the step of applying liquid to the thermoplastic fiber sheet before or after application will be described.

The timing at which the liquid is applied to the thermoplastic fiber sheet is appropriately determined based on the shape, size, etc. of the object, the application mode, and the like.

For example, when a thermoplastic fiber sheet is wound around a plurality of wires with a small radius of curvature at the ends, if the sheet is forcibly bent in the absence of liquid, the cellulosic fibers may break. There is a risk of leaving traces of bending. Therefore, in this case, the liquid is attached to the thermoplastic fiber sheet before attaching the thermoplastic fiber sheet to the object.

On the other hand, for an object with a gently curved surface or a flat object, regardless of the timing, that is, after attaching a dry thermoplastic fiber sheet to the object, the thermoplastic sheet may be adhered to the object, or the thermoplastic fiber sheet to which the liquid is adhered may be adhered to the object.

The liquid may be attached to the thermoplastic fiber sheet on the entire thermoplastic fiber sheet or on a portion of the thermoplastic fiber sheet (for example, the edge where floating is a problem).

The “liquid” to be adhered is not particularly limited as long as it does not substantially dissolve the thermoplastic resin fibers. Here, "substantially not dissolved" means that even if the thermoplastic resin fibers are stirred in a liquid at 25° C. for 1 minute, the weight loss of the thermoplastic resin after stirring is 5% by weight or less. Examples of such liquid media include water and ethanol.

<Step of removing liquid from thermoplastic fiber sheet: liquid removing step>
Next, the process of removing the liquid from the thermoplastic fiber sheet will be described.

This step is performed prior to the heat-sealing step, which will be described later. However, liquid removal and thermal fusion may be performed simultaneously by heating.

Note that liquid removal can be performed by a known technique such as applying air or heat. Preferable examples include a means of exposing to a high temperature (eg, a temperature higher than room temperature (eg, 25° C.)) (eg, hot air drying).

<Step of heat-sealing the thermoplastic fiber sheet to the object: heat-sealing step>
Next, the process of heat-sealing the thermoplastic fiber sheet to the object will be described.

Thermal fusion bonding can be performed by a well-known technique, for example, by heat-pressing (thermocompression bonding) a thermoplastic fiber sheet for an extremely short period of time. Also, the shape can be maintained by fixing only the ends.

Here, when a thermoplastic resin fiber having a softening temperature of 100° C. or higher and 140° C. or lower is used as a raw material for a thermoplastic fiber sheet, it can be fixed to an object by thermal fusion bonding at a low temperature.

Here, "thermal fusion bonding at a low temperature" is preferably performed at a heating temperature of 140°C or less for a heating time of 10 minutes or less, and at a heating temperature of 120°C or less for a heating time of 5 minutes or less. It is more preferable to carry out the heating, and it is even more preferable to carry out the heating at a temperature of 100° C. or less and for a heating time of 3 minutes or less. The lower limit of the heating temperature is, for example, the softening temperature or higher, and the lower limit of the heating time is, for example, several seconds (eg, 3 seconds).

Moreover, the pressure during thermocompression bonding is not particularly limited, but is preferably 0.1 MPa or more.

<<Use of thermoplastic fiber sheet>>
The thermoplastic fiber sheet according to the present invention is useful as a sheet for thermocompression bonding. For example, the thermoplastic fiber sheet according to the present invention can be used for binding (for fixing wire harnesses), for protecting wire harnesses, and for heat press molding (for IC cards, IC tags, contact type or non-contact type with built-in thin batteries). communication media, etc.), simple joining by thermocompression, decorative molding, film insert molding, and building materials such as waterproof wallpaper.

<<Manufacturing example>>
(Example 1)
Copolyester fibers (softening temperature: 110° C., fineness: 2 dtex, fiber length: 5 mm, main fibers), which are thermoplastic resin fibers, were sufficiently dispersed in water in advance. Cellulosic fibers beaten with NBKP and adjusted to a Canadian standard freeness of 650 ml are gradually added into the copolymer polyester fiber slurry (divided into 4 times, and after waiting 10 minutes or more after each addition). Then, a papermaking slurry was produced. Copolyester fiber and NBKP were added in amounts of 50 parts by weight each.

In the papermaking process, the degree of vacuum in the suction vacuum chamber was set to 600 mmHg, and suction was carried out as gently as possible.

In the drying process after papermaking, the surface temperature of the Yankee dryer was set to 120° C., and the amount of water vapor in the steam chamber was maintained at 80 to 100 RH% by reducing the exhaust amount of the exhaust fan.

(Examples 2 to 7, Comparative Examples 1 to 4)
The thermoplastic fiber sheets according to Examples 2 to 7 and Comparative Examples 1 to 3 and the cellulosic fiber sheet according to Comparative Example 4 were prepared in the same manner as in Example 1 except that the raw materials were blended as shown in Table 1. Obtained.

<<Test example>>
The sheets according to Examples and Comparative Examples were evaluated for shape stability, water retention rate, WET strength and adhesive strength. Table 1 shows the results. Since the methods for evaluating the water retention rate, WET strength, and adhesive strength have been described above, the method for evaluating shape stability will be described below.

<Shape stability>
The shape stability test is a test to confirm whether the temporary fixation is firm.

(Measuring method)
Here, the shape stability was evaluated under the following three patterns (conditions 1 to 3).

Condition (1): With water immersion In this test, the sheets (wet state) according to the outline, the examples and the comparative examples are wound around a cylinder to obtain a dried primary fixed body. After that, this is a test to confirm the shape retention property immediately after the primary fixing body is removed from the cylinder and after being left for a predetermined time (normal temperature and normal pressure).

Here, if the shape maintainability is sufficient, the primary fixed body (sheet), including the ends, follows the winding shape even after the primary fixed body is removed from the cylinder (that is, the ends of the sheet) follow the winding shape. (because there is no float), the winding shape is maintained (that is, the outer diameter of the cylinder and the inner diameter of the primary fixed body are substantially the same). On the other hand, if the shape retention is insufficient, after the cylinder is removed after winding, the end of the sheet does not follow the winding shape (that is, there is a float at the end). The shape is unraveled (that is, the inner diameter of the primary fixed body becomes larger than the outer diameter of the cylinder).

To explain the above in detail, first, a thermoplastic fiber sheet (sample) is cut into 10 mm×200 mm. The sample is immersed in tap water (temperature: 20°C, time: 10 seconds). Excess water is then removed from the submerged sample with dry Bemcot. Next, the sample is wound around a vinyl chloride cylinder of 25 mm in diameter (using a tension gauge, the tension is fixed at 7 N, and the sample is wound while being careful not to pull it too much and break it). The ends of the rolled sample are then clipped with eye clips. Then, air-drying is performed for 30 minutes at room temperature (25° C.) with an air blower. After that, remove the eyeball clip and remove the primary fixing body from the PVC cylinder. Immediately thereafter, measure the internal diameter of the primary fixture with a ruler. After that, the primary fixed body is left at room temperature for 30 minutes, and then the inner diameter is measured again.

Condition (2): Immersed in water, dried at 50°C Removed from the vinyl chloride cylinder in the same manner as condition (1), except that normal temperature (25°C) air drying was changed to 50°C heat drying (oven drying). The inner diameter of the primary fixed body is measured immediately after and after being left at room temperature for 30 minutes.

Condition (3): With ethanol immersion The internal diameter of the primary fixed body immediately after removal from the vinyl chloride cylinder and after standing at room temperature for 30 minutes was performed in the same manner as condition (1) except that the immersion liquid was changed from water to ethanol. to measure.

(Evaluation criteria)
◎: 25mm
○: More than 25 mm and less than 30 mm △: 30 mm or more and less than 35 mm ×: 35 mm or more and impracticable

<Water retention rate>
The water retention rate was measured based on the measurement method described above. Evaluation criteria are as follows.

(Evaluation criteria)
◎: 80% or more and 220% or less ○: 70% or more and less than 80% △: 50% or more and less than 70%, more than 220% ×: less than 50%

<Wet strength>
The WET intensity was measured based on the measurement method described above. Evaluation criteria are as follows.

(Evaluation criteria)
◎: 10 N / cm or more and 17 N / cm or less ○: 8 N / cm or more and less than 10 N / cm, 17 N / cm or more and 18 N / cm or less △: 7 N / cm or more and less than 8 N / cm, 18 N / cm or more and less than 20 N / cm ×: 0 N/cm or more and less than 7 N/cm, 20 N/cm or more

<Adhesion strength>
Adhesion strength was measured based on the measurement method described above. Evaluation criteria are as follows.

(Evaluation criteria)
◎: 1.5 N / cm or more ○: 1.2 N / cm or more and less than 1.5 N / cm ×: 0 N / cm or more and less than 1.2 N / cm

In the above evaluation criteria, regarding the shape stability, for any of the conditions (1) to (3), if the evaluation at the time of 0 minutes elapsed is from ⊚ to △, it can withstand practical use. It should be noted that the evaluation after 30 minutes has passed is preferably from ⊚ to △ or higher from the viewpoint of ease of setting working conditions. Other than the shape stability, ⊚ to △ are practical levels.

As described above, the thermoplastic fiber sheets of Examples 1 to 7 exhibited sufficient shape stability under the conditions of immersion in water and an elapsed time of 0 minutes. Further, the thermoplastic fiber sheets of Examples 1 to 4 and Examples 6 and 7 showed excellent effect of exhibiting shape stability even when immersed in water for an elapsed time of 30 minutes. In addition, even when the immersion liquid was changed to ethanol (organic solvent), high morphological stability was exhibited. That is, all of the thermoplastic fiber sheets of Examples 1 to 7 are very useful at least under working conditions in which the working time from temporary fixing to heat melting (permanent fixing) is relatively short. shown.

On the other hand, the thermoplastic fiber sheet of Comparative Example 1, in which the weight ratio of cellulosic fibers and thermoplastic resin fibers exceeds 6.5/3.5 and the WET strength is lower than 7 N/cm, is Since the sheet was broken by the tension of , the shape stability could not be evaluated. The plastic fiber sheets of Comparative Examples 2 to 4, in which the weight ratio of the cellulosic fiber and the thermoplastic resin fiber is less than 2/8 and the WET strength is more than 20 N/cm, are immersed in water and have the same shape even when the elapsed time is 0 minutes. could not demonstrate stability.

Claims (4)

It is composed of at least cellulosic fibers and thermoplastic resin fibers, and the weight ratio of the cellulosic fibers to the thermoplastic resin fibers (the cellulosic fibers: the thermoplastic resin fibers) is 6.5:3.5. A thermoplastic fiber sheet with a ratio of ~2:8 and a WET strength of 7N
/ cm or more and less than 20 N/cm, a thermoplastic fiber sheet for a wire harness protector . The thermoplastic fiber sheet according to claim 1, wherein the thermoplastic fiber sheet has a water retention rate of 50 to 220%. 2. The thermoplastic resin fibers are main fibers made of one or more thermoplastic resins.
or the thermoplastic fiber sheet according to 2. The thermoplastic fiber sheet is used to temporarily fix the thermoplastic fiber sheet to an object, and then permanently fix the thermoplastic fiber sheet to the object by thermally fusing the thermoplastic resin fibers. The thermoplastic fiber sheet according to any one of claims 1 to 3, which is a