JP3295201B2 - Syringe barrel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a syringe barrel having an improved wall thickness.

[0002]

2. Description of the Related Art As shown in FIG. 3, a syringe barrel having a tip at the center of the tip of the barrel to which a hub of an injection needle formed integrally with the barrel can be fitted is known. ing.

[0003] Conventionally, when such a syringe outer cylinder is formed by injection molding, the core portion of the mold is inclined by the pressure generated when the molten resin flows into the mold, and the wall thickness of the cylinder becomes thicker. Tends to occur. In order to prevent the uneven thickness, two or three gate positions are provided at the tip of the outer cylinder or at the intersection of the outer cylinder tip and the outer wall surface of the outer cylinder to allow the resin to flow into the mold. Further, as a technique for improving the uneven wall thickness of the cylindrical body wall surface, a method of providing a gate position at a portion where the tip end surface of the cylindrical body and the tip portion are joined (Japanese Patent Publication No. 61-5046)
No. 1 publication).

[0004]

When a mold for a cold runner is used in molding a syringe barrel, resin in the runner is wasted. Also, since the cooling time of the runner part is relatively long and the molding cycle is long,
There was a problem in terms of production costs.

As a means for solving the above problems, there is a method using a hot runner mold.

When a hot runner mold is used, waste of the resin in the runner portion is eliminated, and the molding cycle can be remarkably shortened, so that a syringe outer cylinder excellent in production cost can be obtained.

However, when a plurality of gate positions are provided in a hot runner mold, the mold manufacturing cost is increased, and the effect of heat generation from the hot runner chip on the product part is increased, and molding defects are likely to occur. For this reason, it is desirable that the gate position be one point.

[0008] However, the syringe outer cylinder conventionally injection-molded with one gate position is disadvantageous in that the thickness of the wall of the cylinder body is significantly greater than that of the injection-molded cylinder using a plurality of gates. Generally, radiation such as gamma rays, electron beams, and X-rays is used to sterilize syringes.At this time, the radiation decomposes and degrades the resin. Decrease significantly,
It is easily broken by impact. According to Japanese Patent Publication No. Sho 61-50461, it is possible to improve the uneven thickness of the syringe outer cylinder even when the gate position is set to one point. This method is not preferable because the structure of the mold becomes extremely complicated, and it is difficult to design a practical mold. Further, the mold is greatly affected by the heat generated by the hot runner chip, and molding defects are likely to occur.

Therefore, it is a problem to be solved to obtain a syringe outer cylinder which can be injection-molded at one gate position on the front end face of the cylinder and has a small wall thickness of the cylinder body.

[0010]

Means for Solving the Problems In view of these problems, the present inventors have conducted intensive studies and as a result, by effectively providing a thickness distribution on the tip end surface of the cylindrical body, the wall thickness of the cylindrical body is reduced. The present inventors have found that a very small syringe barrel can be obtained by injection molding of a one-point gate, and have come to propose the present invention.

That is, the present invention relates to a syringe outer cylinder having a tip portion projecting from the center of the front end face of a cylindrical body and made of a thermoplastic resin, wherein a gate position for molding is set at one end on the front end face of the cylindrical body.
In the cylindrical tip surface of the syringe outer cylinder viewed from the axial direction, the center point is O, the distance from O to the cylinder inner wall surface is a, Where b is the distance to the intersection line and c is the distance from O to the center of the gate position, the radius is a about O, the central angle is 30 degrees, and the line is symmetrical with respect to a straight line connecting O and the center of the gate position. The average value of the plate thickness in a range that is inside the circular sector and outside the circle with the radius c around O is defined as t1, and further, inside the circle with the radius c around O and around O When the average value of the plate thickness in a range outside the circle having the radius b is t2,
A syringe outer cylinder characterized by satisfying the following expression: t2 / t1 ≧ 1.2.

FIG. 1 shows a distal end face of the syringe outer cylinder of the present invention when viewed from the axial direction thereof, and FIG. 2 shows a cross section taken along a plane parallel to the axial direction. In FIGS. 1 and 2, O is a center point. The distance from O to the cylinder inner wall surface P is a, the distance from O to the intersection line between the tip outer wall surface Q and the cylindrical tip surface R is b, and the distance from O to the gate position center S is c. . At this time, the radius around O is a, the central angle is 30 degrees, the inside is a fan-shaped line symmetrical with respect to a straight line connecting O and the gate position center, and the outside is a circle having a radius c around O. The average value of the plate thickness in the range (the portion of the grid line in FIG. 1) is defined as t1, and further, a range inside the circle having the radius c centered on O and outside the circle having the radius b centered on O ( It is necessary that the average value of the sheet thickness of the hatched portion in FIG. 1) is t2, and that t1 and t2 satisfy the following expression: t2 / t1 ≧ 1.2.

When t2 / t1 <1.2, when the resin is allowed to flow from a single point gate into a mold cavity composed of a male mold and a female mold during molding of the syringe barrel, The resin flows into the cylindrical wall surface closer to the position than the cylinder wall surface farther from the gate position, and the male mold tilts due to the pressure difference due to the resin flow. Becomes very large.

As long as the plate thicknesses of the grid line portion and the hatched portion shown in FIG. 1 satisfy the above relationship, the shape and size of the thin and thick portions are not particularly limited. , May be deformed. For example, as shown in FIGS. 4 and 5, the central angle of the sector of the thin portion may be greater than 30 degrees, and the shape of the thick portion does not need to be ring-shaped, as shown in FIG. It may be a shape having protrusions at both ends of the ring. In any case, it is important that the average values t1 and t2 of the plate thickness in the above-mentioned range satisfy the above-mentioned relationship. It is preferable that t1 and t2 satisfy t2 / t1 ≧ 1.4 in order to further reduce uneven thickness of the outer wall of the cylindrical body.

Further, as shown in FIG. 2, t2 / t1 ≧
When 1.2 is satisfied, the thickness of the outer cylinder tip surface may be continuously changed, or the thickness may be changed stepwise.

When a hot runner is used, if the hot runner is located near the chip portion, the mold structure of the gate portion becomes extremely complicated, making practical die design difficult. Since molding defects are likely to occur, the gate position of the hot runner should be 0.4 ≧ c / a ≧
Preferably, it is provided in the range of 0.8.

As the thermoplastic resin for forming the syringe barrel according to the present invention, known thermoplastic resins can be used without any limitation. In particular, a polyolefin resin is preferable in consideration of physical properties such as chemical resistance, heat resistance, transparency, and radiation resistance. For example, homopolyethylene, homopolypropylene,
Propylene ethylene copolymer, propylene ethylene butene copolymer, propylene butene copolymer, ethylene butene copolymer, and blends of these resins and blends of these resins with different resins such as vinyl acetate There may be. Further, conventionally known additives such as an antioxidant, a light stabilizer, a colorant, an antistatic agent, a lubricant, and a nucleating agent may be added to the thermoplastic resin used in the present invention.

[0018]

The syringe barrel of the present invention has a good appearance and a function as a syringe barrel since the wall thickness of the barrel is small, and the mechanical strength due to radiation sterilization is small. Since injection molding can be performed by a one-point gate using a hot runner mold, the production cost of the mold is low, the waste of resin in the runner portion is small, and the molding cycle can be significantly shortened. The production cost can be significantly reduced as compared with the syringe outer cylinder. Therefore, it is extremely useful as an outer cylinder of a disposable syringe.

[0019]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

The polypropylene resin used in Examples and Comparative Examples was a propylene-ethylene copolymer (ethylene content 1.8 wt%, melt flow index 23 g /
10 minutes) For 100 parts by weight, 0.03 parts by weight of a phenolic antioxidant, 0.07 parts by weight of a phosphoric acid antioxidant,
0.05 parts by weight of a light stabilizer and 0.08 parts by weight of a lubricant were added. Examples and Comparative Examples (A) Molding Method FIG. 4, FIG. 5 and FIG. 2 were manufactured using the above polypropylene resin under the following conditions using a 150t injection molding machine manufactured by Japan Steel Works, Ltd.
Injection molding of an outer cylinder as shown by was performed.

Injection molding temperature (cylinder set temperature) 220 ° C. Mold temperature (cooling water set temperature) 25 ° C. The dimensions and angles are a = 7.0 mm, b =
2.4mm, c = 4.8mm, d = 8.6mm, e = 2.0mm, f = 0.82mm, g = 84.6
mm, h = 1.5mm, i = 1.5mm, j = 75 degrees, k = 1.2mm, l = 1.5mm, m =
85 degrees. 4 and 5, the plate thickness in a region other than the hatched portion and the grid line portion was 1.0 mm.

In order to confirm the effect of the present invention, as shown in Table 1, syringe outer cylinders having different thickness distributions of the outer cylinder tip surface were prepared, and 5 mm from the intersection line between the cylinder tip surface and the outer wall surface of the cylinder. The thickness deviation was measured by calculating the difference between the maximum value and the minimum value of the wall thickness of the entire outer circumference of the cylindrical body at a distance of.

[0023]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a view of a distal end face of a cylindrical body when a syringe outer cylinder is viewed from an axial direction.

FIG. 2 is a cross-sectional view of a distal end portion of a cylindrical body taken along a plane parallel to an axial direction of a syringe outer cylinder.

FIG. 3 is a schematic view of the syringe barrel of FIG. 3;

FIG. 4 is a view of the distal end surface of the cylindrical body of the syringe outer cylinder of the embodiment when viewed from the axial direction.

FIG. 5 is a view of the distal end surface of a cylindrical body of the syringe outer cylinder of the embodiment when viewed from an axial direction.

[Explanation of symbols]

 O: center P: inner wall surface of cylinder Q: outer wall surface of tip R: tip surface of cylinder S: center of gate position

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-11868 (JP, A) JP-A-59-11869 (JP, A) JP-A-4-29816 (JP, A) JP-A-59-11886 90564 (JP, A) JP-A-61-142137 (JP, A) JP-A-4-366604 (JP, A) JP-A-4-67251 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61M 5/18-5/31

Claims (1)

(57) [Claims] 1. A syringe outer cylinder made of a thermoplastic resin, having a tip portion protruding at the center of a front end surface of a cylindrical body, and having a gate position for molding on the front end surface of the cylindrical body, On the distal end surface of the cylindrical body viewed from the axial direction of the syringe outer cylinder, the center point is O, the distance from O to the inner wall surface of the cylinder is a, and the distance from O to the intersection line between the outer wall surface of the tip portion and the distal end surface of the cylindrical body. The distance of b,
When the distance from O to the center of the gate position is c, O
The thickness of the plate within a range in which the radius around the center is a, the central angle is 30 degrees, and the inside of the sector that is line-symmetric with respect to the straight line connecting O and the gate position center and outside the circle with the radius c around O When the average value is t1 and the average value of the plate thickness in a range inside the circle having the radius c around O and outside the circle having the radius b around O is t2, the following expression is obtained. A syringe barrel that satisfies t2 / t1 ≧ 1.2.