Abstrict The present invention relates to a biodegradable disposable syringe
and more particularly, to the biodegradable disposable syringe by
using a novel polyester resin composition under a specific injection
molding condition, thus being able to be disposed of without causing
environmental contamination.
Claims What is claimed is:
1. A polyester resin produced by the esterification and condensation
of: 1) an aromatic dicarboxylic acid or an acid anyhdride thereof;
2) succinic acid or adipic acid; and 3) 14-butanediol or ethylene
glycol, wherein the polyester has a biodegradability of at least
about 90%.
2. The resin of claim 1 wherein the polycondensation is performed
under 0.3 torr at 245.degree. C. for at least 155 minutes.
3. The resin of claim 1 wherein as starting esterification reagents
were used succinic acid and 14-butanediol with a catalyst.
4. The resin of claim 1 wherein the polycondensation was performed
for at least 200 minutes.
5. A process for producing a polyester, said process comprising
the steps of: esterification of succinic acid and 14-butanediol
to yield an esterification product; and polycondensation of the
esterification product under 0.3 torr at 245.degree. C. for at least
155 mm to yield a polyester having a biodegradability of at least
about 90%.
6. The process of claim 5 wherein in the esterification, adipic
acid is provided as a further reagent.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a biodegradable disposable syringe
and more particularly, to the biodegradable disposable syringe by
using a novel polyester resin composition under a specific injection
molding condition, thus being able to be disposed of without causing
environmental contamination.
2. Description of the Related Art
In general, biodegradable resins have been welcomed worldwide since
they can be disposed of without causing environmental contamination
and thus their uses are on the gradual increase these days.
There have been known various kinds of biodegradable resins, however,
they have not been applicable to commercial products because either
their applications were too limited or their physical properties
and biodegradability were not well qualified for good molding and
quality products.
The aliphatic polyester, known to have a good biodegradable property
(J of Macromol. SCI-Chem., A-23(3), 1986 pp. 393-409), have been
used as materials in medical, agricultural, fishing and packaging
industries and its fields of applications are on gradual growth.
However, the conventional type of aliphatic polyesters had disadvantages
that their backbone structures were too soft and heat-labile, it
had low crystallinity, low melting point, difficulty in molding
due to high melt index, poor tensile strength and tear strength.
To make these aliphatic polyesters more applicable, many efforts
have been exerted to increase the number average molecular weight
of the current aliphatic polyester to have more than 30000 however,
it has not been able to obtain aliphatic polyester having a molecular
weight greater than 15000 in the conventional polycondensation
system.
As a way to solve these problems conventional polyesters, a method
of manufacturing aliphatic polyester resin having a number average
molecular weight of greater than 30000 by adjusting factors such
as reaction temperature, degree of vacuum and amount of catalysts
was disclosed in Korean Unexamined Patent Publication No 95-758;
however, said aliphatic polyester resin had a low weight average
molecular weight and was also heat-labile thus not considered appropriate
in molding or forming.
In Korean Unexamined Patent Publication No 95-114171 a method
of manufacturing aliphatic polyester with a high molecular weight
by incorporating a monomer such as a polyhydric alcohol or a poly
(at least tri-) hydric carboxylic acid is disclosed. The above process
provided a way to improve the molding and forming properties of
the aliphatic polyester resin by introducing the monomers into the
reactor to reduce the reaction time and to diffuse the molecules
within the product. However, the application of this type of polyester
resin was not easy due to the decrease of physical properties such
as tensile strength resulted from the drastic increase in low molecular
weight polyesters. Besides, the fact that the polyester resin easily
becomes a gel type makes it difficult to control the reaction for
preparing the polyester resin. There is still another process for
increasing the molecular weight of the aliphatic polyester resin.
Unexamined Korean Patent Publication No. 95-25072 which discloses
the high molecular weight aliphatic polyester resin produced by
an isocyanate as a coupling material reacting to an aliphatic polyester
resin having a number average molecular weight of 15000 to 20000
which is produced by dehydration or de-glycol reaction of the mixture
of main materials of (1) an aliphatic(including cyclic type), and
(2) an aliphatic (including cyclic type) dicarboxylic acid(or an
anhydride thereof) with or without (3) a little of monomer of polyhydric
alcohol or polyhydric carboxylic acid (or acid anhydride thereof).
The aliphatic polyester resin obtained in this way had a number
average molecular weight of 20000 to 70000. However, the above-mentioned
process has a few drawbacks that it requires more reaction time
thus resulting in poor productivity, and the isocyanate, a coupling
material to increase the molecular weight of polyester resin, is
known to be a carcinogen so necessitating an extremely careful handling
of the ingredient.
On top of that there has not been found a good resolution how to
deal with the waste disposal of syringes nor the syringes ever manufactured
by using biodegradable polyester resins.
SUMMARY OF THE INVENTION
The conventional disposable syringes used in medical fields have
been a cause of environmental contamination while its biodegradable
versions have been experiencing the limited applications due to
their poor physical properties. The object of the invention is therefore
to provide a disposable syringe which can not only be degraded in
nature without causing an environmental contamination but be applied
in a broader field of medical industry by having superior physical.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a biodegradable disposable syringe manufactured according
to the method of the present invention.
DESCRIPTION OF THE INVENTION
The present invention relates to a disposable syringe manufactured
by means of injection molding using biodegradable polyester resin
having 9000-90000 of number average molecular weight, 30000-600000
of weight average molecular weight, 40-150.degree. C. of melting
point, 0.1-50 g/10 min of melt index (190.degree. C., 2160 g).
The resin composition used in the present invention comprises an
aromatic dicarboxylic acid(or an acid anhydride thereof such as
dimethyl terephthalate and terephthalic acid; an aliphatic (including
cyclic type) dicarboxylic acid(or an acid anhydride thereof), one
or more selected from the group consisting of succinic acid and
adipic acid; and an aliphatic (including cyclic type) glycol, one
or more selected from the group consisting of 14-butanediol and
ethylene glycol, by means of esterification and polycondensation
reactions as disclosed in Unexamined Korean Patent Publication Nos
98-33837 98-3383499-56991 and 99-58816.
The polyester resin in the present invention is an aliphatic polyester
resin which has superior physical properties sufficient to resolve
the limitations used to be present in the conventional biodegradable
types of resins by improved biodegradability ascribed to its peculiar
molecular structure.
The specific physical properties of the biodegradable polyester
resin in the present invention can be represented as shown in the
following Table 1.
TABLE 1 Injection Tensile Strength Elongation Biodegradability
MP(.degree. C.) (.degree. C.) (kg/cm.sup.2) (%) (%) 40-70 130-140
330 700 98 90 140-150 350 700 96 100 150-160 400 600 94 110-150
160-170 400 300 90
According to the present invention, the appropriate melting point
of the resin ranges from 40 to 150.degree. C., preferably from 100
to 150.degree. C. If the melting point is below the above range
the forming becomes hard to adjust properly due to low crystallinity.
Products manufactured by means of injection molding as in the syringe
of the present invention are used in general for producing relatively
hard and durable parts, and those polyester resins with higher melting
point will be more suitable for injection molding. If the temperature
of injection molding is too low, the resulting syringe products
will become too soft to retain its physical properties. The melting
point of conventional polypropylene plastic materials falls between
180 and 220.degree. C. and thus the properties of those materials
are totally different from the one in the present invention.
Injection molding using the biodegradable resins of the present
invention may be performed under general temperature conditions,
however, the preferred temperature ranges from 120 to 190.degree.
C. If the molding is performed at a temperature lower than 120.degree.
C. it is hard to produce a desirable product because the resin kept
within the screw will not be completely melted, while physical properties
become poor due to heat decomposition if it is performed at a temperature
higher than 190.degree. C. The conventional PP resin for syringes
has different injection molding temperature range, 230-275.degree.
C. However, if the resins in the present invention are molded under
temperatures use for conventional resins, the resins will be inappropriate
for molding because they will decomposed by heat and their physical
properties will become extremely poor. Further, if the resins in
the present invention are kept to stay within the screw of injection
for more than 10 min the molding cannot be well proceeded or the
molded product would not be able to carry the proper properties
of syringe if they are molded due to heat decomposition.
For the production of highly durable syringes, the resin may be
combined with a strength fortifying additive selected from the group
consisting of talc, calcium carbonate, magnesium stearate, calcium
sulfate, starches, sugar powder, particular anhydrous silicate and
calcium phosphate, and preferably by adding 1-60 wt. % of talc or
calcium carbonate based on the 100 wt. % of resin, which then enables
to improve the strength of the resins in the present invention comparable
to the conventional resins such as polypropylene, polystyrene or
ABS resin. Calcium carbonate is inferior to talc in fortifying strength,
however, it can serve as a fertilizer and prevent the soils from
acidifying when it becomes biodegraded and left on the surface of
soils after burial. In addition, the combustion rate of calcium
carbonate added resin was better than those of resin alone or talc-added
resin in the present invention.
The syringes produced in accordance with the present invention
can be produced in various forms disposable syringe, pre-filled
type syringe, general syringe and the like.
For example, FIG. 1 shows a biodegradable disposable syringe of
the present invention having a needle cap 1 a barrel 2 and a plunger
3 manufactured by using a polyester resin composition of the present
invention under a specific injection molding condition with the
exception of the needle.
The following examples are intended to be illustrative of the present
invention and should not be construed as limiting the scope of this
invention defined by the appended claims.
Preparation Example 1
To a 500 mL Erlenmeyer's flask filled with nitrogen gas 118 g of
succinic acid, 121.7 g of 14-butanediol and 0.1 g of tetrabutyltitanate
as a catalyst, were added while slowly increasing the temperature
until it reached 200.degree. C. When the temperature reached 200.degree.
C., the reaction mixture was allowed to react for 2 hrs and then
theoretical mass of water was effused. Then 0.1 g of antimony acetate,
0.2 g of dibutyltin oxide, 0.07 g of tetrabutyltitanate as catalysts,
and 0.2 g of trimethyl phosphate as a stabilizer were added. The
temperature was raised and a polycondensation reaction was performed
under 0.3 torr at 245.degree. C. for 155 min. The sample of biodegradable
resin taken at this point had a melt index of 15 (190.degree. C.,
2160 g), number average molecular weight of 31000 weight average
molecular weight of 190000 and melting point of 117.degree. C.
as measured by DSC method.
Preparation Example 2
To a 500 mL Erlenmeyer's flask filled with nitrogen gas, 5.9 g
of succinic acid, 6.3 g of 14-butanediol and 0.1 g of tetrabutyltitanate
as a catalyst were added to carry esterification by effusing water
while slowly increasing the temperature. When the temperature reached
200.degree. C., theoretical mass of water was effused completely
to give 8.6 g of aliphatic low molecular weight polymer with its
molecular weight around 10000. Then, 76.1 g of terephthalic acid,
135.2 g of 14-butanediol, and 0.2 g of tetrabutyltitanate a catalyst
were added to the reaction mixture to carry esterification by effusing
methanol while slowly increasing the temperature. After methanol
was effused completely while keeping the temperature at 205.degree.
C., 29.5 g of succinic acid and 43.8 g of adipic acid were added
to carry further esterification. After water was effused while keeping
the temperature at 180.degree. C., 0.1 g of antimony trioxide, 0.3
g of dibutyltin oxide, 0.07 g of tetrabutyltitanate as catalysts,
and 0.2 g of trimethyl phosphate as a stabilizer were added. The
temperature was raised until it reached 245.degree. C. and a polycondensation
reaction was performed under 0.3 torr at 245.degree. C. for 200
min. The sample of biodegradable resin taken at this point had a
melt index of 2 (190.degree. C., 2160 g), number average molecular
weight of 61000 weight average molecular weight of 290000 and
melting point of 117.degree. C. as measured by DSC method.
Example 1.about.2
Disposable syringes were manufactured by using polyester resins
having 117.degree. C. of melting point produced in the above Preparation
Examples 1 and 2 under 130-140.degree. C. by means of injection
molding. The test results of syringes showed that 400 kg/cm.sup.2
and 410 kg/cm.sup.2 for tensile strength, 300% and 320% for elongation,
and 90% and 92% for biodegradability rate after 45 days, respectively.
The biodegradability was measured by Organic Waste Systems[O.W.S.n.v.](Dok
Noord 4 B-9000 Gent, Belgium), and tensile strength and elongation
were measured by UTM. |