JP5237758B2 - Resin molded product and manufacturing method thereof - Google Patents

Description

  The present invention relates to a resin molded product made of a synthetic resin containing short fibers and having a sub-thin portion bent or branched with respect to a main thin portion and a method for producing the same.

  Conventionally, in a resin molded product using a liquid crystal polymer (LCP) or the like as a molding material, a composite with a fiber is generally performed in order to reduce anisotropy due to orientation.

  In addition, as a resin molded product having a thin portion having a thickness of 1 mm or less, for example, as shown in Non-Patent Document 1, a liquid crystal comprising a thin resin molded product having a thickness of 1.0 mm and containing short fibers having a fiber length of about 200 μm. A polymer is disclosed as a raw material.

The non-patent document 1 does not include a sub-thin portion having a thickness of 1.0 mm or less protruding in a direction intersecting from the main thin-wall portion, but conventionally a resin having a main thin portion and a sub-thin portion having a thickness of 1 mm or less. None of the molded products and their manufacturing methods focus on the fiber length and fiber length distribution of the short fibers contained in the resin material. In such resin molded products, the tensile strength and the bending rigidity of the sub-thin portion are reduced. The linear expansion coefficient sometimes increased.
“Molding”, October 20, 2003, Japan Society for Plastic Molding, Volume 15, 698-705.

  The present invention has been made in view of the above-described conventional problems, and has a main thin part and a sub thin part, and has improved tensile strength and bending rigidity, and has a reduced linear expansion coefficient and a method for manufacturing the same. It is an issue to provide.

前記体積分率Ｖ_ｌに対する体積分率Ｖの割合Ｖ／Ｖ_ｌを４０％以上とすることを特徴とする。 In order to solve the above-mentioned problem, the resin molded product according to claim 1 of the present invention is made of a synthetic resin containing the short fibers 2 and integrally protrudes in a direction intersecting from the main thin portion 3 and the main thin portion 3. It includes a sub-thin portion 4 upstream end and comprising projecting base end of the time of molding is connected to the main thin portion 3, both 1.0mm or less the thickness t ₁ and the thickness t ₂ of the sub-thin portion 4 of the main thin wall portion 3 In the resin molded product
A portion located upstream of the intersection 5 with the sub thin portion 4 in the main thin portion 3 is defined as an upstream thin portion 6 and an angle formed by the upstream thin portion 6 and the sub thin portion 4 is defined as θ. The critical fiber length L _c derived from the following formula 3 among all the contained short fibers 2 (where L _f in formula 3 is the average fiber length of the fractured fibers when the tensile test is carried out) The volume fraction of the above short fibers 2 with respect to all the short fibers 2 is V _l , the volume length of the short fibers 2 with the fiber length not less than the critical fiber length L _{c and not} more than L _max derived by the following formula 1 with respect to all the short fibers 2. Let the rate be V,

The ratio V / V _l of the volume fraction V to the volume fraction V _l is 40% or more.

  A second aspect of the present invention is characterized in that, in the first aspect, the corner 13 formed by the upstream thin portion 6 and the auxiliary thin portion 4 is formed in a linear or arc-shaped chamfered shape.

上流側薄肉部６の副薄肉部４と反対側の面における仮想直線Ａが通過する部分、又は、副薄肉部４の上流側薄肉部６と反対側の面における仮想直線Ａが通過する部分のうち、少なくとも一方に短繊維逃がし用突部１５を形成して成ることを特徴とする。 A third aspect of the present invention is the first or second aspect, wherein the upstream thin portion 6 is inclined toward the auxiliary thin portion 4 by an angle φ derived by the following expression 2 and the upstream thin portion 6 and the secondary thin portion 6 are Draw a virtual straight line A that touches the surface of the corner 13 formed by the thin portion 4 only at one place,

The portion of the upstream thin portion 6 through which the virtual straight line A passes on the surface opposite to the sub thin portion 4 or the portion of the sub thin portion 4 opposite to the upstream thin portion 6 through which the virtual straight line A passes. Of these, the short fiber escape projection 15 is formed on at least one of the above.

  A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the short fiber 2 is made of a flexible organic fiber having a melting point higher than that of the matrix resin.

前記体積分率Ｖ_ｌに対する体積分率Ｖの割合Ｖ／Ｖ_ｌを４０％以上とすることを特徴とする。 The method for producing a resin molded product according to claim 5 is a synthetic resin injection-molded product containing the short fibers 2, and is integrally formed in a direction intersecting with the main thin portion 3 and the main thin portion 3. comprising an upstream end and comprising projecting proximal end during molding to protrude are connected to the main thin portion 3 sub thin portion 4, the thickness t ₁ and the thickness t ₂ of the sub-thin portion 4 of the main thin portion 3 are both 1. In the method for manufacturing a resin molded product of 0 mm or less, the mold 7 of the resin molded product 1 forms a main cavity portion 8 that forms the main thin portion 3 and a sub cavity portion 9 that forms the sub thin portion 4, A portion of the main cavity portion 8 located upstream from the intersection 10 with the sub-cavity portion 9 is defined as an upstream-side cavity portion 11, and an angle formed by the upstream-side cavity portion 11 and the sub-cavity portion 9 is defined as θ. Of all the short fibers 2 contained in the synthetic resin, the fiber length is critical. V _{l is the} volume fraction of all short fibers 2 of short fibers 2 that are equal to or longer than fiber length L _{c, and the} critical fiber length L _c is derived from the following equation 3 (where L _f in equation 3 is a tensile test) The volume fraction of all short fibers 2 of the short fibers 2 that is equal to or greater than the average fiber length of the broken fibers when carried out and is equal to or less than L _max derived from the following equation 1 is V,

The ratio V / V _l of the volume fraction V to the volume fraction V _l is 40% or more.

  A sixth aspect of the present invention is characterized in that, in the fifth aspect, the protruding corner portion 12 formed by the upstream cavity portion 11 and the sub-cavity portion 9 is formed in a linear or arc-shaped chamfered shape.

上流側キャビティ部１１の副キャビティ部９と反対側の内面における仮想直線Ａが通過する部分、又は、副キャビティ部９の上流側キャビティ部１１と反対側の内面における仮想直線Ａが通過する部分のうち、少なくとも一方に、短繊維逃がし用凹部１４を形成して成ることを特徴とする。 A seventh aspect of the present invention is the same as the fifth or sixth aspect, wherein the upstream cavity portion 11 is inclined toward the sub-cavity portion 9 by an angle φ derived from the following equation 2 and the upstream-side cavity portion 11 is Draw an imaginary straight line A that touches the surface of the protruding corner 12 formed by the cavity 9 only at one location,

The portion of the inner surface of the upstream cavity portion 11 opposite to the sub cavity portion 9 through which the virtual straight line A passes, or the portion of the sub cavity portion 9 on the inner surface of the opposite side of the upstream cavity portion 11 through which the virtual straight line A passes. Among these, at least one is characterized in that a short fiber escape recess 14 is formed.

  An eighth aspect is characterized in that, in any one of the fifth to seventh aspects, the short fibers 2 are made of flexible organic fibers having a melting point higher than that of the matrix resin.

Invention provides a resin molded article having a sub-thin portion projecting from the thickness 1.0mm or less of the main thin wall portion and the main thin portion, the fiber length of the short fibers of more than the critical fiber length L _c volume according to claim 1 By setting the ratio V / V ₁ of the volume fraction V of the short fibers whose fiber length to the fraction V ₁ is not less than the critical fiber length L _{c and not} more than L _max to 40% or more, the tensile strength of the resin molded product can be increased. In addition, it projects in a direction intersecting the main thin part and is thin, so that it is difficult to fill the short fiber at the time of molding. Bending rigidity can be increased.

In addition to the effect of the above-mentioned claim 1, the invention according to claim 2 is characterized in that the corner formed by the upstream thin portion and the sub thin portion is formed into a linear or arc-shaped chamfered shape, thereby forming a fiber during molding. Short fibers whose length is longer than L _max can be smoothly flowed to the sub-cavity side forming the sub-thin portion, and the sub-thin portion is filled with more short fibers to increase the bending rigidity of the sub-thin portion. Can do.

In addition to the effect of the first or second aspect, the invention according to claim 3 is directed from the upstream cavity portion forming the upstream thin portion to the sub cavity portion forming the sub thin portion during molding. The molten resin containing the short fiber flows, and at this time, the end of the short fiber contained in the molten resin can be released to the short fiber escape recess forming the short fiber escape projection, and the fiber length is L _max It is possible to smoothly flow a short fiber longer than the sub-cavity side. For this reason, it is possible to increase the bending rigidity of the sub-thin portion by filling the sub-thin portion with more short fibers.

In the invention according to claim 4, in addition to the effect of any one of claims 1 to 3, the short fiber contained in the resin molded product is a flexible organic fiber, so that at the time of molding The molten resin containing short fibers flows from the upstream cavity portion forming the upstream thin portion to the sub cavity portion forming the sub thin portion. At this time, the short fibers contained in the molten resin contact the inner surface of the mold. As a result, short fibers having a fiber length longer than _Lmax can be smoothly caused to flow toward the subcavity 9 side. For this reason, it is possible to increase the bending rigidity of the sub-thin portion by filling the sub-thin portion with more short fibers.

In the invention according to claim 5, in forming a resin molded product having a main thin part having a thickness of 1.0 mm or less and a sub thin part protruding from the main thin part, the fiber length is a short fiber having a critical fiber length _Lc or more. Resin produced by setting the ratio V / V ₁ of the volume fraction V of short fibers whose fiber length to the fiber volume fraction V _l is not less than the critical fiber length L _{c and not} more than L _max to 40% or more The tensile strength of the molded product can be increased, and the bending strength of the sub-thin wall part formed by the sub-cavity part can be increased by filling the sub-cavity part where short fibers do not easily flow into the sub-cavity part. Can be increased.

In the invention according to claim 6, in addition to the effect of the invention according to claim 5, the projecting corner portion formed by the upstream cavity portion and the sub-cavity portion is formed in a linear or arc-shaped chamfered shape, thereby forming In some cases, short fibers having a fiber length longer than L _max can be smoothly flowed to the cavity forming the sub-thin portion. For this reason, it is possible to increase the bending rigidity of the sub-thin portion by filling the sub-thin portion with more short fibers.

In the invention according to claim 7, in addition to the effect of claim 5 or claim 6 described above, molten resin containing short fibers flows from the upstream cavity portion toward the sub-cavity portion at the time of molding. the end of the short fibers contained in the molten resin can be released to the short fibers relief recesses, fiber length can flow smoothly long short fiber than L _max the sub cavity portion. For this reason, it is possible to increase the bending rigidity of the sub-thin portion by filling the sub-thin portion with more short fibers.

According to an eighth aspect of the present invention, in addition to the effect of any one of the fifth to seventh aspects, in molding, a sub-cavity that forms a sub-thin portion from an upstream-side cavity portion that forms the upstream-side thin portion at the time of molding. The molten resin containing short fibers flows in the part. At this time, the short fibers contained in the molten resin are deformed in contact with the inner surface of the mold, and thereby the short fibers having a fiber length longer than _Lmax are transformed into the sub cavity portion 9. Can flow smoothly to the side. For this reason, it is possible to increase the bending rigidity of the sub-thin portion by filling the sub-thin portion with more short fibers.

  Hereinafter, the present invention will be described with reference to the accompanying drawings.

  The present invention is applied to, for example, a resin molded product that constitutes the body of an electronic device such as a connector that is mounted on a substrate by reflow mounting and has terminals arranged at a narrow pitch. Of course, the resin molded product to which the present invention is applied is not limited to this.

(Embodiment 1)
The resin molded product 1 is made of a synthetic resin containing short fibers 2 (fibrous fillers), and is formed by injection molding with an injection molding machine using resin pellets containing short fibers as a molding material.

  The synthetic resin used as the matrix resin of the resin molded product 1 is made of a liquid crystal polymer (LCP), and a preferable resin is a thermoplastic resin such as 6 nylon (PA6), 6-6 nylon (PA6-6), 4 Polyamide such as aromatic polyamide (PA6T, PA9T, etc.) such as -6 nylon (PA46), 11 nylon (PA11), 6-10 nylon, PA-MXD-6, polyphthalamide, or polyphenylene sulfide or polyphenylene ether Or a polyetherketone, a polyketone such as polyetheretherketone, a polyester such as polyethylene terephthalate (PET) or polybutylene terephthalate, a polyetherimide, or a polyimide.

  As the short fibers 2 serving as a reinforcing material, for example, inorganic fibers such as glass fibers and carbon fibers are used.

  The resin molded product 1 is a thin-walled injection-molded product. As shown in FIG. 1B, a main thin-walled portion 3 and a protruding base that integrally protrudes in a direction intersecting from the main thin-walled portion 3 and serves as an upstream end during molding. An auxiliary thin portion 4 having an end connected to the main thin portion 3 is provided.

  Both thin portions 3 and 4 are formed in a thin plate shape having a uniform thickness with the depth direction in FIG. 1B being the width direction. The sub-thin portion 4 protrudes perpendicularly from one surface of the main thin portion 3, that is, a portion located on the upstream side from the intersection 5 with the sub-thin portion 4 in the main thin portion 3 (closer to the gate trace side) If the portion) is the upstream thin portion 6, the angle θ formed by the upstream thin portion 6 and the sub thin portion 4 is 90 degrees. The auxiliary thin portion 4 protrudes from the middle of the length direction of the main thin portion 3 (left and right direction in FIG. 1 (b)), and constitutes a rib whose protruding end is a free end.

The main thickness _{t 2} of the thickness _{t 1} and the sub-thin portion 4 of the thin portion 3 are both 1.0mm or less _{(t 1} ≦ 1.0mm, _{t 2} ≦ 1.0mm), and more specifically, the thickness t ₁ and t ₂ are both 0.5 mm or less (t ₁ ≦ 0.5 mm, t ₂ ≦ 0.5 mm).

  FIG. 1A is an enlarged view of a portion where both thin portions 3 and 4 are formed in the cavity formed by the mold 7 of the resin molded product 1. As shown in the figure, the mold 7 is formed with a main cavity portion 8 communicating with the gate and a sub cavity portion 9 communicating with the main cavity portion 8.

  A space having the same shape as the main thin portion 3 is formed inside the main cavity portion 8, and the main thin portion 3 is formed by the main cavity portion 8. A space having the same shape as the sub thin portion 4 is formed inside the sub cavity portion 9, and the sub thin portion 4 is formed by the sub cavity portion 9.

  Hereinafter, the portion located on the upstream side (gate side) of the main cavity portion 8 with respect to the intersecting portion 10 with the sub cavity portion 9 is referred to as an upstream cavity portion 11. That is, the upstream side thin portion 6 is formed by the upstream side cavity portion 11.

  When molding the resin molded product 1, a molten resin containing the short fibers 2 is injected from a gate (not shown), and the molten resin is filled into the main cavity portion 8 and the subcavity portion 9 of the mold 7. At this time, the molten resin containing the short fibers 2 flows into the upstream cavity portion 11 from the end opposite to the sub-cavity portion 9 in the length direction of the upstream cavity portion 11, and thereafter, the intersection portion 10 and branches into the sub-cavity portion 9 and the downstream portion of the main cavity portion 8 with respect to the intersecting portion 10. That is, of the two flows of molten resin branched at the intersection 10, the flow from the upstream cavity 11 to the sub-cavity 9 through the intersection 10 changes the direction of the angle θ at the intersection 10.

なお、式１におけるθは前述した上流側薄肉部６と副薄肉部４とでなす角度、又は、これと同角度となる上流側キャビティ部１１と副キャビティ部９とでなす角度である。 Here, in the present invention, the fiber length distribution of the short fibers 2 contained in the resin molded product 1 is as follows. That is, of all of the short fibers 2 contained in the synthetic resin forming the resin molded article 1, the fiber length is critical fiber length L _c over the volume fraction relative to the total short fibers 2 of the short fibers 2 V _l, fibers If the length is and the volume fraction relative to the total short fiber 2 of L _max following short fibers and V at the critical fiber length L _c above, a ratio V / V _l occupied volume fraction V against the volume fraction V _l 40% That's it.

In Equation 1, θ is an angle formed by the upstream thin portion 6 and the sub thin portion 4 described above, or an angle formed by the upstream cavity portion 11 and the sub cavity portion 9 having the same angle.

（ここで、Ｌ_ｆ；破断繊維の平均繊維長）
上記式１により導き出されるＬ_ｍａｘは、図１（ａ）に示すように、直線状の短繊維２が上流側キャビティ部１１に対して下記式（２）によって導き出される角度φ傾斜し、且つ、短繊維２の両端が、上流側キャビティ部１１の副キャビティ部９と反対側の内面１１ａ（つまり上流側薄肉部６の副薄肉部４を突出した側と反対側の面を形成する内面）と、副キャビティ部９の上流側キャビティ部１１と反対側の内面９ａ（つまり副薄肉部４の上流側薄肉部６側の面を形成する内面）の夫々に接すると共に、短繊維２の中央が上流側キャビティ部１１と副キャビティ部９とでなす出隅部１２の頂点１２ａに接した状態における短繊維２の繊維長である。

Further, the critical fiber length _Lc is obtained by performing a tensile test of a test piece prepared from a molded product, obtaining the fiber length distribution of only the broken fiber from the difference in fiber length distribution before and after the test, and calculating by the following formula 3. Is.

(Where L _{f is} the average fiber length of the broken fibers)
As shown in FIG. 1A, L _max derived from the above equation 1 is inclined by an angle φ derived from the linear short fiber 2 by the following equation (2) with respect to the upstream cavity portion 11, and Both ends of the short fiber 2 have an inner surface 11a opposite to the sub-cavity portion 9 of the upstream cavity portion 11 (that is, an inner surface forming a surface opposite to the side protruding the sub-thin portion 4 of the upstream thin portion 6). The inner surface 9a of the sub cavity portion 9 opposite to the upstream cavity portion 11 (that is, the inner surface forming the surface of the sub thin portion 4 on the upstream thin portion 6 side) is in contact with each other, and the center of the short fiber 2 is upstream. This is the fiber length of the short fiber 2 in a state where it is in contact with the apex 12a of the protruding corner portion 12 formed by the side cavity portion 11 and the sub cavity portion 9.

Therefore, the fiber length of the short fibers 2 shorter than L _max, the short fibers 2 gold contained in the molten resin reaches the secondary cavity 9 from the upstream side cavity 11 through the crossing portion 10 during the molding This means that physical interference with the inner surface of the mold 7 is prevented, and the short fibers 2 are easy to flow toward the subcavity 9 side.

（ここで、Ｓ_ｍ；樹脂の引張強度、Ｖ_ｉ；臨界繊維長Ｌ_ｃ以下の短繊維の体積分率、Ｖ_ｌ；臨界繊維長Ｌ_ｃ以上の短繊維の体積分率、Ｌ_ｉ；臨界繊維長Ｌ_ｃ以下の短繊維の長さ、Ｌ_ｌ；臨界繊維長Ｌ_ｃ以上の短繊維の長さ、τ；界面せん断応力、σ；短繊維の破断強度、ｒ；短繊維の半径） Further, as shown by the following formula 4, if there are many long short fiber 2 than the critical fiber length L _c in the resin molded article 1, the tensile strength of the resin molded article 1 is increased.

(Where S _m ; tensile strength of resin, V _i ; volume fraction of short fibers having critical fiber length L _c or less, V _l ; volume fraction of short fibers having critical fiber length L _c or more, L _i ; critical The length of short fibers having a fiber length L _c or less, L _l ; the length of short fibers having a critical fiber length L _c or more, τ: interfacial shear stress, σ: breaking strength of short fibers, r: radius of short fibers)

Thus, the tensile strength of the resin molded product 1 can be increased by setting the ratio V / V _l of the volume fraction V to the volume fraction V _l to 40% or more. Further, in this case, the short fibers 2 contained in the molten resin from the upstream cavity portion 11 to the sub cavity portion 9 are difficult to physically interfere with the inner surface of the mold 7. The short fibers 2 can be filled, and the bending rigidity of the auxiliary thin portion 4 can be increased.

That is, as shown by a broken line b in FIG. 3, when the average length of the fiber length distribution of the short fibers 2 is shortened, the short fibers 2 having a fiber length of _Lc or more are decreased, and the tensile strength is decreased. As shown in FIG. 4, when the average length of the fiber length distribution of the short fibers 2 is increased, the short fibers 2 having a fiber length of L _max or more increase and the sub-cavity portion 9 cannot be filled with a lot of short fibers 2. Then, by setting the above V / _Vl to 40% or more, the tensile strength of the resin molded product 1 is improved, and the short cavity 2 is filled into the subcavity portion 9 to increase the bending rigidity of the subthin wall portion 4. Can do it.

In this case, since it often fill a long short fiber 2 than the critical fiber length L _c in the sub-thin portion 4, which is effective in the resin molded article 1 linear expansion coefficient of the sub-thin portion 4 is reduced can be heated .

  Therefore, when the resin molded product 1 is a connector in which the terminal is locked and attached to the sub-thin portion 4, and the terminal is a connector that is reflow-mounted on the substrate, the sub-thin portion 4 is assembled when the terminal is assembled. This is particularly effective because it is difficult to deform and warpage is unlikely to occur during reflow mounting.

(Embodiment 2)
This embodiment is shown in FIG. In the present embodiment, as shown in FIG. 2B, the auxiliary thin portion 4 in the first embodiment protrudes from the end portion in the length direction of the main thin portion 3. That is, in the first embodiment, the sub thin portion 4 protrudes from the middle of the main thin portion 3 in the length direction to have a T-shaped cross section, but in the present embodiment, from the downstream end when the main thin portion 3 is molded. The sub-thin portion 4 protrudes to have an L-shaped cross section.

  Accordingly, when the resin molded product 1 is molded, the flow of the molten resin has an angle θ from the upstream cavity portion 11 to the sub cavity portion 9 via the intersecting portion 10 as shown by the arrow in FIG. It will turn.

(Embodiment 3)
This embodiment is shown in FIG. In this embodiment, as shown in FIG. 4A, the protruding corner portion 12 formed by the upstream cavity portion 11 and the sub-cavity portion 9 of the first embodiment is chamfered, and the protruding corner portion 12 is linearly shaped. It is formed in a chamfered shape. Therefore, as shown in FIG. 4B, the resin molded product 1 of the present embodiment molded by the die 7 has a straight corner 13 formed by the upstream thin portion 6 and the sub thin portion 4. The chamfered shape is formed.

  In this way, the protruding corner portion 12 formed by the upstream cavity portion 11 and the sub-cavity portion 9 is formed into a linear chamfered shape, so that the protruding corner portion 12 is not chamfered as in the embodiment of FIG. In comparison, it has the following advantages.

That is, in the embodiment shown in FIG. 1, the short fiber 2 having a fiber length longer than the short fiber 2 having the fiber length _Lmax shown by the broken line in FIG. Although it is difficult to flow to the cavity portion 9 side, in this embodiment, the protruding corner portion 12 formed by the upstream cavity portion 11 and the sub-cavity portion 9 has a chamfered shape, so that FIG. The short fiber 2 whose fiber length indicated by the solid line is longer than _Lmax can be smoothly flowed to the subcavity 9 side. Therefore, it is possible to increase the bending rigidity of the sub thin portion 4 by filling the sub cavity portion 9 with many short fibers 2.

(Embodiment 4)
This embodiment is shown in FIG. In this embodiment, the protruding corner 12 is formed in a linear chamfered shape in the second embodiment, as in the third embodiment.

(Embodiment 5)
This embodiment is shown in FIG. In the present embodiment, as shown in FIG. 6A, the protruding corner portion 12 formed by the upstream cavity portion 11 and the sub-cavity portion 9 of the first embodiment is chamfered, and the protruding corner portion 12 is arc-shaped chamfered. It is formed into a shape. Therefore, as shown in FIG. 6B, the resin molded product 1 of the present embodiment molded by the mold 7 has an arcuate corner 13 formed by the upstream thin portion 6 and the sub thin portion 4. It is formed in a chamfered shape.

  Thus, by making the protruding corner portion 12 formed by the upstream cavity portion 11 and the sub-cavity portion 9 into an arc-shaped chamfered shape, there is an advantage similar to that of the third embodiment.

(Embodiment 6)
This embodiment is shown in FIG. In the present embodiment, the protruding corner 12 is formed in an arc-shaped chamfered shape in the second embodiment as in the fifth embodiment.

(Embodiment 7)
This embodiment is shown in FIG. In this embodiment, as shown in FIG. 8A, a short fiber escape recess 14 is formed on the inner surface 11a of the upstream cavity 11 of the first embodiment on the opposite side to the sub-cavity 9.

  As shown in FIG. 8A, the short fiber escape recess 14 is positioned at the downstream end of the upstream cavity 11 and is formed into an angular shape formed by the upstream cavity 11 and the sub cavity 9 during molding. It is formed in the position which can accommodate the one end part of the short fiber 2 which contact | connected the vertex 12a of the protruding corner part 12 of this.

  Specifically, as shown in FIG. 8 (a), it is inclined toward the sub-cavity portion 9 by the angle φ derived from the above equation 2 with respect to the length direction of the upstream-side cavity portion 11, and the protruding corner portion. An imaginary straight line A that touches the surface of 12 at only one location is drawn (that is, the imaginary straight line A passes through the vertex 12a of the protruding corner 12), and the imaginary straight line 11a on the inner surface 11a opposite to the subcavity 9 of the upstream cavity 11 A short fiber escape recess 14 having a rectangular cross section is formed in a portion through which the straight line A passes.

  Therefore, the resin molded product 1 of the present embodiment formed by the mold 7 has a short fiber escape protrusion 15 having the same shape as the short fiber escape recess 14 formed by the short fiber escape recess 14. It is formed. That is, as shown in FIG. 8B, the upstream thin portion 6 is inclined toward the sub thin portion 4 by the angle φ derived from the above formula 2 with respect to the length direction of the upstream thin portion 6 and the upstream thin portion 6 An imaginary straight line A that is in contact with the surface of the corner 13 formed by the subthinned portion 4 is drawn only at one location (that is, the imaginary straight line A passes through the vertex 13a of the corner 13). A short fiber escape projection 15 is formed at a portion through which the virtual straight line A passes on the surface opposite to the portion 4.

In the present embodiment, since the short fiber escape recess 14 is formed, at the time of molding, as shown in FIG. 8A, the upstream cavity portion 11 is passed through the intersecting portion 10 to the sub cavity portion 9. through the ends of the short fibers 2 can be released to the short fibers escape recess 14, the fiber length can flow smoothly short fibers 2 longer than L _max the sub cavity 9 side. Therefore, a lot of the short fibers 2 can be filled in the sub cavity portion 9 and the bending rigidity of the sub thin portion 4 can be increased.

(Embodiment 8)
This embodiment is shown in FIG. In the present embodiment, as shown in FIG. 9B, a short fiber escape recess 14 similar to that in the seventh embodiment is formed in the second embodiment.

(Embodiment 9)
This embodiment is shown in FIG. In this embodiment, as shown in FIG. 10A, the short fiber escape recess 14 of Embodiment 8 is formed on the inner surface 9 a of the sub cavity portion 9 on the opposite side to the upstream cavity portion 11.

  As shown in FIG. 10A, the short fiber escape recess 14 is positioned at the upstream end of the sub-cavity 9, and has an angular protruding corner formed by the upstream-side cavity 11 and the sub-cavity 9. It is formed at a position where one end of the short fiber 2 in contact with the apex 12a of the portion 12 can be stored.

  Specifically, the virtual straight line A is drawn in the same manner as in the eighth embodiment, and a short fiber escape having a rectangular cross section is formed in a portion where the virtual straight line A passes through the inner surface 9a on the opposite side of the upstream cavity portion 11 of the sub cavity portion 9. A recess 14 is formed.

  Therefore, the resin molded product 1 of the present embodiment formed by the mold 7 is formed with the short fiber escape protrusion 15 having the same shape as the short fiber escape recess 14 formed by the short fiber escape recess 14. Is done. That is, as shown in FIG. 10 (b), the virtual straight line A is drawn as in the eighth embodiment, and the short fiber is passed through the portion where the virtual straight line A on the surface opposite to the upstream thin portion 6 of the sub thin portion 4 passes. An escape projection 15 is formed.

In the present embodiment, since the short fiber escape recess 14 is formed, as in the seventh embodiment, at the time of molding, as shown in FIG. the end of the short fibers 2 which flows into the sub-cavity 9 through 10 can be released to the short fibers escape recess 14, flow long staple fibers 2 smoothly in the sub-cavity 9 side than the fiber length L _max be able to.

(Embodiment 10)
This embodiment is shown in FIG. In this embodiment, as shown in FIG. 11B, a short fiber escape recess 14 is formed in the second embodiment as in the ninth embodiment.

  In addition, in the said Embodiments 7-10, you may form the protrusion corner part 12 in a chamfering shape similarly to Embodiment 3-6. Further, in Embodiments 7 and 8, the short fiber escape recess 14 of Embodiments 9 and 10 is formed, and the short fiber escape recess 14 is formed in both the upstream cavity portion 11 and the sub cavity portion 9. Be good.

(Embodiment 11)
This embodiment is shown in FIG. In the present embodiment, the short fibers 2 included in the resin molded product 1 of Embodiment 1 are flexible organic fibers having a melting point higher than the melting point of the synthetic resin serving as the matrix resin.

Table 1 lists the organic fibers used as the short fibers 2 and collectively shows the physical properties of each organic fiber.

Thus, by making the short fiber 2 contained in the resin molded product 1 into an organic fiber having flexibility, at the time of molding, as shown in FIG. 12, the upstream cavity portion 11 passes through the intersection portion 10. The short fibers 2 flowing in the sub-cavity portion 9 can be deformed when contacting the inner surface in the vicinity of the intersecting portion 10 of the mold 7, whereby the short fibers 2 whose fiber length is longer than L _max are changed to the side of the sub-cavity portion 9. Can flow smoothly.

Embodiment 12
This embodiment is shown in FIG. In the present embodiment, the short fibers 2 contained in the resin molded product 1 of the second embodiment are made of flexible organic fibers having a melting point higher than that of the synthetic resin serving as the matrix resin, similar to the eleventh embodiment. is there. As the organic fiber, any one of organic fibers shown in Table 1 is used as in the case of the eleventh embodiment.

  In the above-described first to tenth embodiments, flexible organic fibers may be used as the short fibers 2 in the same manner as in the above-described embodiments 11 and 12. In the first to twelfth embodiments, the sub thin portion 4 protrudes perpendicularly to the main thin portion 3 and the angle θ formed by the upstream thin portion 6 and the sub thin portion 4 is 90 degrees. In other words, the protruding direction of the sub-thin portion 4 may be inclined with respect to the length direction of the upstream thin portion 6.

  Next, Examples 1 to 3 and Comparative Examples 1 to 7 will be described.

Example 1
This example is an example corresponding to the first embodiment, and FIG. 14 shows the shape of the resin molded product 1 to be molded. The resin molded product 1 has a main thin portion 3 having a width of 20 mm × a length of 50 mm × a thickness of t ₁ 0.5 mm, and a sub-thin portion having a width of 20 mm × a height of 3 mm × a thickness of t _{2 of} 0.15 mm at a position of 8.3 mm from the gate. Part 4 is connected. In order to align the resin flow direction of the main thin portion 3, the gate was a fan gate and connected to the main thin portion 3 serving as a base without a step.

As the molding material, pellets made of liquid crystal polymer (LCP) containing glass fibers having a fiber diameter of 10 μm and a filling rate of 30% by weight as the short fibers 2 and having a critical fiber length _Lc of 0.5 mm were used. The fiber length distribution actually measured for the resin pellets is shown in FIG.

  The fiber length distribution was measured by placing the material pellets in an alumina crucible (CW-B000, manufactured by Nikkato Co., Ltd.) and capping the material pellets in a muffle furnace (KM-600, manufactured by Advantech Co., Ltd.). The glass fiber was extracted by maintaining in the atmosphere at 120 ° C. for 120 minutes. The fiber length was measured using image processing software (UVS Light, manufactured by Keio Electronics Co., Ltd.).

Molding was performed under the conditions shown in Table 2 below using a pre-plastic injection molding machine (TR20EHV, manufactured by Sodick Plustech Co., Ltd.) having a plunger diameter of 16 mm and a maximum clamping force of 196 kN.

(Example 2)
This embodiment of the thickness _{t 1} of the main thin portion 3 of Example 1 and 0.3 mm, the thickness _{t 2} of the sub-thin portion 4 was set to 0.3 mm. The other points are the same as in the first embodiment.

(Example 3)
This embodiment of the thickness _{t 1} of the main thin portion 3 of Example 1 and 0.5 mm, the thickness _{t 2} of the sub-thin portion 4 was set to 0.3 mm. The other points are the same as in the first embodiment.

(Comparative Example 1)
The thickness t ₁ of the main thin portion 3 was 0.3 mm, and the thickness t ₂ of the sub thin portion 4 was 0.15 mm. The other points are the same as in the first embodiment.

(Comparative Example 2)
As the molding material, pellets made of liquid crystal polymer (LCP) containing glass fibers having a fiber diameter of 10 μm and a filling rate of 30% by weight as the short fibers 2 and having a critical fiber length _Lc of 0.5 mm were used. FIG. 16B shows the fiber length distribution actually measured for the resin pellets. The thickness t ₁ of the main thin portion 3 was 0.15 mm, and the thickness t ₂ of the sub thin portion 4 was 0.15 mm. The other points are the same as in the first embodiment.

(Comparative Example 3)
The thickness t ₁ of the main thin portion 3 was 0.15 mm, and the thickness t ₂ of the sub thin portion 4 was 0.3 mm. Other points are the same as those of Comparative Example 2.

(Comparative Example 4)
The thickness t ₁ of the main thin portion 3 was 0.3 mm, and the thickness t ₂ of the sub thin portion 4 was 0.15 mm. Other points are the same as those of Comparative Example 2.

(Comparative Example 5)
The thickness t ₁ of the main thin portion 3 was 0.3 mm, and the thickness t ₂ of the sub thin portion 4 was 0.3 mm. Other points are the same as those of Comparative Example 2.

(Comparative Example 6)
The thickness t ₁ of the main thin portion 3 was 0.5 mm, and the thickness t ₂ of the sub thin portion 4 was 0.15 mm. Other points are the same as those of Comparative Example 2.

(Comparative Example 7)
The thickness t ₁ of the main thin portion 3 was 0.5 mm, and the thickness t ₂ of the sub thin portion 4 was 0.3 mm. Other points are the same as those of Comparative Example 2.

  Evaluation of bending rigidity and determination of tensile strength in the sub-thin wall portion 4 of each resin molded product 1 obtained in Examples 1 to 3 and Comparative Examples 1 to 7 were performed. Table 3 shows the results.

  As shown in FIG. 15, the bending rigidity evaluation in Table 3 is performed by constraining the main thin-walled portion 3 and then in a constant temperature and humidity room with a temperature of 22 ° C. and a relative humidity of 50%, SAICAS (Surface and Surface) manufactured by Daipurwintes Co., Ltd. Interfacial Cutting Analysis System) After adjusting the semi-cylindrical jig 16 having a radius of 1 mm × width of 21 mm attached to the CN type so as to be in contact with the sub-thin portion 4 at a height of 2 mm from the main thin portion, 5 μm / sec The displacement applied to the sub-thin portion 4 and the load in the moving direction at that time were measured. In addition, the arrow a in FIG. 15 shows the flow direction of resin.

  Further, the linear expansion coefficient measured in Table 3 is a ratio in which the width direction of the auxiliary thin portion 4, that is, the length in the paper thickness direction in FIG. 15 expands.

  As can be seen from the results in Table 3, the resin molded product 1 of the present invention was able to improve the tensile strength, the bending rigidity, and the linear expansion coefficient.

(A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 1 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 2 of this invention, (b) is a principal part expanded side view of a resin molded product. It is a graph which shows fiber length distribution of the short fiber of this invention and Comparative Examples b and c. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 3 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 4 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 5 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 6 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 7 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 8 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 9 of this invention, (b) is a principal part expanded side view of a resin molded product. (A) is explanatory drawing which shows the principal part cross section of the metal mold | die for Embodiment 10 of this invention, (b) is a principal part expanded side view of a resin molded product. It is explanatory drawing which shows the principal part cross section of the metal mold | die for Embodiment 11 of this invention. It is explanatory drawing which shows the principal part cross section of the metal mold | die of Embodiment 12 of this invention. The resin molded product of Example 1 is shown, (a) is a side view, (b) is a top view. It is explanatory drawing which shows the evaluation method of bending rigidity. (A) is a graph which shows the fiber length distribution of Examples 1-3 and the comparative example 1, (b) is a graph which shows the fiber length distribution of the comparative examples 2-7.

DESCRIPTION OF SYMBOLS 1 Resin molding 2 Short fiber 3 Main thin part 4 Sub thin part 5 Crossing part 6 Upstream thin part 8 Main cavity part 9 Sub cavity part 10 Crossing part

Claims (8)

Made of synthetic resin containing short fibers, it has a main thin part and a sub-thin part that protrudes integrally in the direction intersecting from the main thin part and has a protruding base end that becomes the upstream end during molding connected to the main thin part in the main thin portion resin molded article together and 1.0mm or less the thickness t ₁ and the thickness t ₂ of the sub-thin portion,
The portion located upstream from the intersection of the main thin portion with the sub thin portion at the time of molding is defined as the upstream thin portion, and the angle formed by the upstream thin portion and the sub thin portion is defined as θ. Among the fibers, the total length of short fibers whose fiber length is derived from the following formula 3 is equal to or greater than the critical fiber length L _c (where L _f in formula 3 is the average fiber length of the fractured fibers when the tensile test is performed). The volume fraction with respect to the fibers is V _l , and the volume fraction with respect to all short fibers of the short fibers whose fiber length is not less than the critical fiber length L _{c and not} more than L _max derived by the following formula 1 is V,

A resin molded product, wherein a ratio V / V ₁ of the volume fraction V to the volume fraction V ₁ is 40% or more.   2. The resin molded product according to claim 1, wherein a corner portion formed by the upstream thin portion and the sub thin portion is formed in a linear or arcuate chamfered shape. An imaginary straight line that inclines toward the sub-thin portion by an angle φ derived from the following equation 2 with respect to the upstream side thin portion, and is in contact with the face of the corner formed by the upstream side thin portion and the sub-thin portion at only one location. Draw A

At least one of the portion through which the virtual straight line A on the surface opposite to the sub-thin portion of the upstream thin portion passes, or the portion through which the virtual straight line A on the surface opposite to the upstream thin portion of the sub-thin portion passes. The resin molded product according to claim 1, wherein a short fiber escape protrusion is formed on the resin molded product.   4. The resin molded product according to claim 1, wherein the short fibers are made of flexible organic fibers having a melting point higher than that of the matrix resin. This is an injection-molded product of synthetic resin containing short fibers, and the main thin-walled portion and the protruding base end that protrudes integrally in the direction intersecting from the main thin-walled portion and becomes the upstream end during molding are connected to the main thin-walled portion in the sub-thin portion wherein the main thin portion thickness t ₁ and the manufacturing method of the sub-thin portion resin molded article together and 1.0mm or less the thickness t ₂ of which are,
The mold of the resin molded product forms a main cavity part that forms the main thin part and a sub cavity part that forms the sub thin part, and is located upstream of the intersection of the main cavity part and the sub cavity part. The critical fiber length derived from the following equation 3 among all short fibers contained in the synthetic resin, where θ is an angle formed by the upstream cavity portion and the upstream cavity portion and the sub-cavity portion, L _c (where L _f in Equation 3 is the average fiber length of the broken fiber when the tensile test is performed) V _{1 is the} volume fraction of all short fibers, and the fiber length is the critical fiber length L _The volume fraction with respect to all short fibers of short fibers not less than _{c and not} more than L _max derived by the following formula 1 is V,

A method for producing a resin molded product, wherein a ratio V / V ₁ of the volume fraction V to the volume fraction V ₁ is 40% or more.   6. The method for producing a resin molded product according to claim 5, wherein a protruding corner portion formed by the upstream cavity portion and the sub-cavity portion is formed in a linear or arc chamfered shape. An imaginary straight line that is inclined toward the sub-cavity portion by an angle φ derived from the following equation 2 with respect to the upstream-side cavity portion, and that is in contact with the surface of the protruding corner formed by the upstream-side cavity portion and the sub-cavity portion only at one location. Draw A

At least one of a portion through which an imaginary straight line A passes through an inner surface of the upstream cavity portion opposite to the sub-cavity portion or a portion through which an imaginary straight line A passes through the inner surface of the sub-cavity portion opposite to the upstream cavity portion. The method for producing a resin molded product according to claim 5 or 6, wherein a short fiber escape recess is formed.   The method for producing a resin molded product according to any one of claims 5 to 7, wherein the short fibers are made of flexible organic fibers having a melting point higher than that of the matrix resin.

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