JPH01274754A - Dental floss - Google Patents

Abstract

PURPOSE:To prevent cut even if the title dental floss is inserted into between teeth and allowed to pass between teeth in strongly pulled state, by using an extension multifilament made of the superhigh polymer of polyolefine or superhigh polymer of ethylene alpha-olefine copolymer having a specific limiting viscosity. CONSTITUTION:The superhigh polymer of polyolefine or superhigh polymer of ethylene alpha-olefine copolymer which constitutes an extension filament has a limiting viscosity [eta] of 5dl/g or more. Among these, the superhigh polymer of ethylene alpha-olefine copolymer contains the alpha-olefine having at least three carbons in 0.1-20pieces per 1,000 carbons of the polymer. This extension multifilament possesses the superior tensile strength and impact resistance, and possesses the superior creep resistance, waterproofness, and self lubricity. Therefore, the between-teeth part can be cleaned sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to dental floss, more specifically, it is made of multifilaments of ultra-high molecular weight polyolefin or multi-filaments of ultra-high molecular weight ethylene/α-olefin copolymer. This invention relates to dental floss that has excellent tensile strength, impact resistance, water resistance, creep resistance, and ease of use.

A technical view of invention and problems.

Dental floss is used to remove food residue and the like from the interdental area by inserting it into the interdental area, pulling it tightly with your fingers, and passing it through the interdental area.

Conventionally, crimped nylon multifilament has been used as such dental floss. However, nylon dental floss has poor tensile strength or impact resistance, so it often breaks during use.
It is not possible to clean all the interdental areas during the day with a single piece of dental floss, and since it lacks self-lubricating properties, it tends to get caught on the teeth and has a bad feel when used.

For this reason, there is a desire for a dental floss that has excellent tensile strength and impact resistance, as well as excellent creep resistance and excellent usability.

It is already known that a molecularly oriented molded article having high elastic modulus and high tensile strength can be obtained by forming ultra-high molecular weight polyethylene into fibers, tapes, etc. and stretching the fibers. For example, in Japanese Patent Application Laid-Open No. 56-15408,
Spinning dilute solutions of ultra-high molecular weight polyethylene and drawing the resulting filaments is described. Also,
JP-A-59-130313 discloses that ultra-high molecular weight polyethylene and wax are melt-kneaded, the kneaded product is extruded, cooled and solidified, and then stretched, and JP-A-59-187614 describes , it is described that the above melt-kneaded product is extruded, drafted, cooled and solidified, and then stretched.

The present invention is an attempt to solve the problems associated with the prior art as described above, and is to provide a material with excellent tensile strength and impact resistance, as well as excellent creep resistance, water resistance, and usability. The purpose is to provide dental floss with the highest quality.

The first dental floss according to the present invention has an intrinsic viscosity [η]
The second dental floss according to the present invention is characterized in that it is made of a drawn multifilament of an ultra-high molecular weight polyolefin having an intrinsic viscosity [η] of at least 5 dl/g, and a carbon Ultra-high molecular weight ethylene containing an average of 0.1 to 20 α-olefins of number 3 or more per 1000 carbon atoms.
It is characterized by being composed of drawn multifilaments of α-olefin copolymer.

The dental floss according to the present invention is made of a drawn multifilament of the above-mentioned ultra-high molecular weight polyolefin or ultra-high molecular weight ethylene/α-olefin copolymer, and has excellent tensile strength and impact resistance, as well as creep resistance. It also has excellent water resistance, so it will not break even if it is inserted into the interdental area and passed under strong tension. In addition, polyolefin is inherently highly self-lubricating, does not get caught during use, and has an excellent feel when used.

The dental floss according to the present invention will be specifically explained below.

First, the drawn filaments of ultra-high molecular weight polyolefin and the drawn filaments of ultra-high molecular weight ethylene/α-olefin copolymer that constitute the dental floss according to the present invention will be explained.

The drawn filaments used in the present invention are drawn filaments of ultra-high molecular weight polyolefin or drawn filaments of ultra-high molecular weight ethylene/α-olefin copolymer.

Specifically, the ultra-high molecular weight polyolefin constituting the drawn filament used in the present invention includes ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, ultra-high molecular weight poly-1-butene, and two or more types of α-olefins. Examples include molecular weight copolymers. This drawn filament of ultra-high molecular weight polyolefin has excellent tensile strength and impact strength, as well as creep resistance and water resistance.

Further, as the ultra-high molecular weight ethylene/α-olefin copolymer constituting the drawn filament used in the present invention, ultra-high molecular weight ethylene/propylene copolymer, ultra-high molecular weight ethylene/1-butene copolymer, ultra-high molecular weight ethylene/1-butene copolymer, Molecular weight ethylene/4-methyl-1-pentene copolymer, ultra-high molecular weight ethylene/1-hexene copolymer, ultra-high molecular weight ethylene/1-hexene copolymer
-Ultra-high molecular weight ethylene/α-olefin copolymer of ethylene and α-olefin having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, such as octyne copolymer or ultra-high molecular weight ethylene/1-decene copolymer An example is coalescence.

In this ultra-high molecular weight ethylene/α-olefin copolymer, the number of α-olefins having 3 or more carbon atoms is 0.1 to 20, preferably 0.5 to 10 per 1000 carbon atoms of the polymer.
It is more preferably contained in an amount of 1 to 7.

A drawn filament obtained from such an ultra-high molecular weight ethylene/α-olefin copolymer has particularly excellent impact resistance and creep resistance compared to a drawn filament obtained from an ultra-high molecular weight polyethylene.

The ultra-high molecular weight polyolefin or ultra-high molecular weight ethylene/α-olefin copolymer constituting the drawn filament used in the present invention has an intrinsic viscosity [η] of 5 dJ/r.
The above is preferably in the range of 7 to 30 dj/, and the drawn filaments obtained from this copolymer have excellent mechanical properties and heat resistance. That is, since the molecular terminals do not contribute to m-fiber strength and the number of molecular terminals is the reciprocal of the molecular weight (viscosity), a material with a large intrinsic viscosity [η] gives high strength.

The density of the drawn filament used in the present invention is 0.9
40-0.990+r/- preferably 0.960-0.
985r/-, where the density is determined by the standard method (ASTHD).
1505) by the density gradient tube method. The density gradient tube at this time was prepared by using carbon tetrachloride and toluene, and the measurement was performed at room temperature (23° C.).

The dielectric constant (IKH) of the drawn filament used in the present invention
z, 23°C) is 1.4-3.0, preferably 1.8-3.
2.4. And the positive electric dissipation tangent (IKHz, 80℃) is 0
．． 05~o, oos% preferably 0.040~o, oi
o%. Here, the dielectric constant and positive electric dissipation tangent are determined by closely aligning fibers and tape-like molecular oriented bodies in one direction.
It was measured by ASTHD 150 using a film-shaped sample.

The stretching ratio of the drawn filament used in the present invention is 5
~80 times, preferably 10 to 50 times.

The degree of molecular orientation in the drawn filament used in the present invention can be determined by an X-ray diffraction method, a birefringence method, a fluorescence polarization method, or the like. For example, Yukichi Go, Teru Kubo: Industrial Chemistry Magazine Vol. 39, p. 992 (1939) describes in detail the degree of orientation due to half-value, that is, the equation (where Ho is the device of the strongest baratropic surface on the equator The degree of orientation (F) defined as the half width (゛) of the intensity distribution curve along the ring is 0.90 or more, especially 0.9
From the viewpoint of mechanical properties, it is desirable that the molecules be oriented so that the number of particles is 5 or more.

Furthermore, the drawn filament used in the present invention has excellent mechanical properties, with a pressure of 20 GPa or more, especially 30 GPa.
an elastic modulus of a or more; 1. '2GPa or more, especially 1.5G
It has a tensile strength of Pa or more.

The impulse voltage breakdown value of the drawn filament used in the present invention is 110-250 KV/nm, preferably 150-220 KV/city. The impulse voltage breakdown value was measured using the same sample as in the case of the dielectric constant, using a brass (25 mm diameter) JIS type electrode on a copper plate, and increasing the voltage while applying negative impulses in steps of 2 KV/3 times. did.

When the drawn filament used in the present invention is a drawn filament of an ultra-high molecular weight ethylene/α-olefin copolymer, the drawn filament is characterized by extremely excellent impact resistance, breaking energy, and creep resistance. have.

The characteristics of drawn filaments of these ultra-high molecular weight ethylene/α-olefin copolymers are expressed by the following physical properties.

The breaking energy of the drawn filament of the ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention is 8
bg-m, /r or more, preferably 10kr-m/g
That's all.

Further, the drawn filament of the ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention has excellent creep resistance. In particular, it has outstanding creep resistance at high temperatures, which corresponds to the conditions that promote room-temperature creep, and is determined as elongation (%) after 90 seconds at a 30% breaking load and an ambient temperature of 70°C. 7% creep
Below, the creep rate (ε, 5ec-1) after 90 seconds to 180 seconds is 4X10-'
sec and below, there are 5 x 10-''sec-' and below.

Among the drawn filaments used in the present invention, the drawn filaments of ultra-high molecular weight ethylene/α-olefin copolymer have the above-mentioned room temperature physical properties, but in addition to these room temperature properties, they also have the following thermal properties. If you have the following characteristics,
It is preferable because the above-mentioned physical properties at room temperature are further improved and heat resistance is also excellent.

The drawn filament of the ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention has at least one crystal melting peak (T11) at a temperature at least 20°C higher than the original crystal melting temperature (Tn) of the copolymer. ) based on the heat of fusion of 15% or more, preferably 20% or more, especially 30%
That's all.

Ultra-high molecular weight ethylene copolymer original crystal melting temperature (TI
) can be determined by a second run in a so-called differential scanning calorimeter, in which the drawn filament is completely melted, cooled to relax the molecular orientation in the drawn filament, and then heated again. can.

To explain further, in the drawn filament used in the present invention, there is no crystal melting peak at all in the aforementioned crystal melting temperature range inherent to the copolymer, or even if it exists, it exists only as a very slight tailing. . The crystal melting peak (Tp) is generally in the temperature range Tll1+20
°C to Tra+50°C5, especially T111+b, and this peak (Tp) often appears as a plurality of peaks within the above temperature range. That is, this crystal melting peak (Tp) is within the temperature range T
High temperature side melting peak ('rp 1) in I+35℃~Tm-1-100℃ and temperature range Ti+20℃~Tll
It often appears as two separate peaks, the low-temperature side melting peak ('rp2) at 1+35°C, and depending on the manufacturing conditions of the drawn filament, Tpl and Tp2 may further consist of a plurality of peaks.

These high crystal melting peaks ('rp 1, 'rp
2) is thought to significantly improve the heat resistance of drawn filaments of ultra-high molecular weight ethylene/α-olefin copolymers and contribute to strength retention or elastic modulus retention after high-temperature thermal history. It will be done.

Further, the total amount of heat of fusion based on the high temperature side melting peak (Tpl) in the temperature range T11+35°C to TI+100°C is 1. - It is desirable that the content be 5% or more, especially 3.0% or more.

In addition, as long as the sum of the heat of fusion based on the high temperature 111 melting peak (Tpl) satisfies the above value, if the high temperature side melting peak (Tpl) does not stand out as a main peak, that is, it is a collection of small peaks. Alternatively, even if the peak becomes broad, the heat resistance may be slightly lost, but the creep resistance is excellent.

The melting point and heat of crystal fusion in the present invention were measured by the following method.

The melting point was determined using a differential scanning calorimeter as follows.

A DSCII type (manufactured by PerkinElmer) was used as a differential scanning calorimeter. The sample size is approximately 3 cm, 4 rm x 4 nm,
The orientation direction was restrained by wrapping the sample around an aluminum plate having a thickness of 0.2 mm.The sample, which was then wrapped around the aluminum plate, was sealed in an aluminum pan and used as a sample for measurement. Additionally, the empty aluminum pan that is usually placed in the reference holder was filled with the same aluminum plate used for the sample to maintain heat balance. First, the sample was held at 30°C for about 1 minute, then at 10°C.
The temperature was raised to 250°C at a heating rate of /min, and the melting point measurement at the first heating was completed, and then the temperature was raised at 250°C for 10
The sample was held at 30°C for 10 minutes, then the temperature was lowered at a rate of 20°C/min, and the sample was held at 30°C for 10 minutes.

Then, the second temperature increase was made to 250°C at a heating rate of 10°C/min.
At this time, the melting point measurement during the second temperature increase (second run) was completed. If the melting point is determined by the maximum value of the melting peak as a six-shoulder, draw a tangent at the inflection point immediately on the low-temperature side and the inflection point immediately on the high-temperature side of the shoulder, and take the intersection as the melting point.

In addition, the straight line (
Draw a perpendicular line to the point 20°C higher than the original crystalline melting temperature (TI) of the ultra-high molecular weight ethylene copolymer, which is determined as the main melting peak during the second temperature rise (baseline), and the area on the low temperature side surrounded by these. is based on the crystal melting (TI) inherent to the ultra-high molecular weight ethylene copolymer, and the high temperature side part is based on the crystal melting (Tp) that exhibits the function of a drawn filament, and the heat of crystal fusion for each is as follows: Calculated from these areas. Also, Tpl and Tp
The heat of fusion based on the melting of TI+
The part surrounded by the perpendicular line from 20°C and the perpendicular line from TIl + 35°C is the heat of fusion based on the melting of TI)2, and the high temperature side part is calculated in the same way as the heat of fusion based on the melting of Tpl. Na.

The drawn filament of the ultra-high molecular weight ethylene/α-olefin copolymer of the present invention has a strength retention rate of 95% or more and an elastic modulus retention rate of 90% or more after being subjected to a heat history of 5 minutes at 170°C. In particular, it has an excellent heat resistance of 95% or more, which is completely unrecognizable in conventional drawn polyethylene filaments.

The molecular orientation of the ultra-high molecular weight polyolefin is t2 with the above-mentioned high elasticity,
As a method for obtaining a drawn ultra-high molecular weight polyolefin product having high tensile strength, for example, JP-A-56-15408
No. 1, JP-A-58-5228, JP-A-59-
130313, JP-A-59-187614, etc., ultra-high molecular weight polyolefin is made into a dilute solution, or low-molecular weight compounds such as paraffin waxes are added to ultra-high molecular weight polyolefin. For example, a method of improving the drawability of ultra-high molecular weight polyolefin and drawing it to a high ratio can be exemplified.

Production of oriented molded product of ultra-high molecular weight ethylene/α-olefin copolymer Next, the present invention will be explained below in order of raw materials, production method, and purpose for easy understanding.

仄-11 The ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention is prepared by slurry polymerizing ethylene and an α-olefin having 3 or more carbon atoms in an organic solvent using a Ziegler catalyst. It can be obtained by

As the α-olefin having 3 or more carbon atoms, propylene,
butene-1, pentene-1,4-methylpentene-1,
Hexene-1, heptene-1, octene-1, etc. are used, and among these, butene-1,4-methylpentene-1, hexene-1, octene-1, etc. are particularly preferred.

Such α-olefins are copolymerized with ethylene in the amount stated above per 1000 carbon atoms of the resulting copolymer. Further, the ultra-high molecular weight ethylene/α-olefin copolymer used as a base when producing the molecularly oriented product in the present invention should have a molecular weight corresponding to the above-mentioned intrinsic viscosity [η].

The α-olefin component in the ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention is determined using an infrared spectrophotometer (manufactured by JASCO Corporation). Specifically, the absorbance at 1378 am-', which represents the bending vibration of the methyl group of the α-olefin incorporated into the ethylene chain, was measured using an infrared spectrophotometer, and this value was determined in advance by 13C nuclear magnetic resonance. Using the equipment, quantify the amount of α-olefin in the ultra-high molecular weight ethylene/α-olefin copolymer by converting it into the number of methyl branches per 1000 carbon atoms using a calibration curve created using a model compound. .

In the present invention, when producing a molecularly oriented product from the ultra-high molecular weight ethylene/α-olefin copolymer, a diluent is added to the copolymer. As such a diluent, a solvent for the ultra-high molecular weight ethylene copolymer or various wax-like substances having compatibility with the ultra-high molecular weight ethylene copolymer can be used.

Such a solvent has a boiling point higher than the melting point of the copolymer, more preferably 20°C higher than the melting point of the copolymer.
A solvent having a boiling point higher than that is used.

Specifically, such solvents include n-nonane, n-
- Decane, n-undecane, n-dodecane, n-tetradecane, n-octadecane or liquid paraffin, aliphatic hydrocarbon solvents such as kerosene, xylene, naphthalene,
Tetralin, butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene, pentylbenzene,
Aromatic hydrocarbon solvents such as dodecylbenzene, bicyclohexyl, decalin, methylnaphthalene, ethylnaphthalene or hydrogenated derivatives thereof, 1,1,2.2-tetrachloroethane, pentachloroethane, hexachloroethane, 1.2.3- Examples include halogenated hydrocarbon solvents such as 1-dichloropropane, dichlorobenzene, 1.2.4-trichlorobenzene, and bromobenzene, and mineral oils such as paraffinic process oil, naphthenic process oil, and aromatic process oil.

Further, as the wax as a diluent, specifically, an aliphatic hydrocarbon compound or a derivative thereof is used.

Such aliphatic hydrocarbon compounds are mainly composed of saturated aliphatic hydrocarbon compounds, and are usually compounds called paraffin waxes having a molecular weight of 2,000 or less, preferably 1,000 or less, more preferably 800 or less.

Specifically, such aliphatic hydrocarbon compounds include n-alkanes having 22 or more carbon atoms such as tocosan, tricosane, tetracosane, and triacontane, or mixtures containing these as main components with lower n-alkanes; So-called paraffin wax separated and refined from petroleum, medium/low pressure polyethylene wax, high pressure polyethylene wax, ethylene copolymer wax, which is a low molecular weight polymer obtained by copolymerizing ethylene or ethylene with other α-olefins, or Waxes obtained by reducing the molecular weight of polyethylene such as medium- and low-pressure polyethylene and high-pressure polyethylene by thermal degradation, oxides of these waxes, oxidized waxes modified with maleic acid, and waxes modified with maleic acid are used.

Examples of aliphatic hydrocarbon compound derivatives include, for example, one or more carboxyl groups, preferably one to two carboxyl groups, particularly preferably one carboxyl group, at the terminal or inside of an aliphatic hydrocarbon group (alkyl group, alkenyl group), A compound having a functional group such as a hydroxyl group, a carbamoyl group, an ester group, a meltcapto group, or a carbonyl group with a carbon number of 8 or more, preferably a carbon number of 12 to 50 or a molecular weight of 130 to 2000.
Preferably, 200 to 800 fatty acids, aliphatic alcohols, fatty acid amides, fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, aliphatic getons, etc. are used.

Examples of such aliphatic hydrocarbon compound derivatives include fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, lauric alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol. Fatty acid amides such as caprinamide, lauramide, palmitinamide, and stearylamide, fatty acid esters such as stearyl acetate, and the like are used.

The ultra-high molecular weight ethylene/α-olefin copolymer and diluent differ depending on their type, but - 3 for boat fishing
:97-80 :20, especially 15:85-60:40
used in a weight ratio of If the amount of the diluent is lower than the above range, the melt viscosity will become too high, making melt kneading and melt molding difficult, and the resulting molded product will have a markedly rough surface and is prone to stretch breakage. On the other hand, if the amount of the diluent is larger than the above range, melt-kneading will become difficult, and the resulting molded product will have poor stretchability.

Melt kneading is generally carried out at 150-300°C, particularly at 170-200°C.
It is carried out at a temperature of 70°C. If the temperature is lower than the above range, the melt viscosity will be too high, making melt molding difficult.If the temperature is higher than the above range, the molecular weight of the ultra-high molecular weight ethylene/α-olefin copolymer will decrease due to thermal degradation. decreases,
It becomes difficult to obtain a molded article having excellent high elastic modulus and high strength. Furthermore, the formulation is made using a Henschel mixer, V
It may be carried out by dry blending using a mold blender or the like, or it may be carried out using a single screw extruder or a multi-screw extruder.

Melt molding of a dope (spinning stock solution) comprising an ultra-high molecular weight ethylene/α-olefin copolymer and a diluent is generally performed by melt extrusion molding. Specifically, filaments for drawing are obtained by melt extruding Dogue through a spinneret.

At this time, drafting, that is, stretching in the molten state can be applied to the molten material extruded from the spinneret. Extrusion speed V of the molten resin within the die orifice. The ratio of the winding speed V of the cooled and solidified undrawn material can be defined as a draft ratio by the following formula.

Draft ratio -V/Vo (2) This draft ratio varies depending on the temperature of the mixture, the molecular weight of the ultra-high molecular weight ethylene copolymer, etc., but is usually 3 or more, preferably 6 or more. can.

Next, the ultra-high molecular weight ethylene α obtained in this way
- Stretching the unstretched molded olefin copolymer. Stretching is carried out so as to effectively impart at least uniaxial molecular orientation to the unstretched molded article obtained from the ultra-high molecular weight ethylene/α-olefin copolymer.

The unstretched molded product obtained from the ultra-high molecular weight ethylene/α-olefin copolymer is generally stretched at 40 to 160°C.
In particular, it is carried out at a temperature of 80-145°C. As a heat medium for heating and maintaining the unstretched molded body at the above-mentioned temperature, any of air, water vapor, and a liquid medium can be used.

However, as a heat medium, a liquid medium that is a solvent capable of eluting and removing the diluent described above and whose boiling point is higher than the melting point of the molded article composition, specifically, decalin, decane, kerosene, etc., is used. It is preferable to carry out the stretching operation in such a manner that the diluent described above can be removed, uneven stretching will not occur during stretching, and a high stretching ratio can be achieved.

The means for removing the diluent from the ultra-high molecular weight ethylene/α-olefin copolymer is not limited to the above-mentioned method, but may include a method of treating an unstretched material with a solvent such as hexane, heptane, hot ethanol, chloroform, or benzene, and then stretching it; A stretched product with high elastic modulus and high strength can also be obtained by removing the diluent in the molded product by treating the stretched product with a solvent such as hexane, heptane, hot ethanol, chloroform, or benzene.

The stretching operation can be performed in one stage or in multiple stages of two or more stages. The stretching ratio depends on the desired molecular orientation and the associated effect of increasing the melting temperature, but -i is 5 to 5.
80 times, preferably 10 to 50 times.

In general, it is preferable to carry out the stretching operation in two or more stages, and in the -th stage, the stretching operation is carried out while extracting the diluent in the extrudate at a relatively low temperature of 80 to 120°C. From the second stage onward, it is preferable to stretch the molded body at a temperature of 120 to 160°C and at a temperature higher than the first stage stretching temperature.

In the case of a uniaxial stretching operation, tension stretching may be performed between rollers having different circumferential speeds.

The drawn filament thus obtained can be heat treated under constrained conditions if desired.

This heat treatment is generally carried out at 140-180°C, preferably at 15°C.
At a temperature of 0 to 175°C for 1 to 20 minutes, preferably 3 to 1
It can be done for 0 minutes. The heat treatment further advances the crystallization of the oriented crystal parts, shifts the crystal melting temperature to a higher temperature side, improves the strength and elastic modulus, and further improves the creep resistance at high temperatures.

In the present invention, a plurality of such drawn filaments of ultra-high molecular weight polyolefin or ultra-high molecular weight ethylene/α-olefin copolymer are bundled, usually 5 to 300, to form a drawn multifilament and used for dental floss.

At this time, to prevent the monofilament from falling apart,
Wax can also be used to further improve lubricity. Moreover, in order to further improve the feeling of use, flavoring agents such as mint can also be used.

Effects of the Invention As described above, in the present invention, ultra-high molecular weight polyolefin,
Alternatively, dental floss uses drawn multifilaments made of ultra-high molecular weight ethylene/α-olefin copolymer, so it has excellent tensile strength and impact resistance, as well as creep resistance, water resistance, and self-lubricating properties. . Therefore, even if the dental floss according to the present invention is inserted into the interdental region and passed through the interdental area under strong tension, it will not break and is also comfortable to use. In addition, when a stretched multifilament like the one described above is used as dental floss, it becomes flat and easy to insert into the interdental area, but it also spreads out in the interdental area.
The interdental area can be thoroughly cleaned.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

! "Polymerization of ultra-high molecular weight ethylene/butene-1 copolymer> Slurry polymerization of ultra-high molecular weight ethylene/butene-1 copolymer was carried out using a Ziegler catalyst and n-decane 1j as a polymerization solvent. Ta. 6 Polymerization is a reaction in which a mixed monomer gas with a molar ratio of ethylene and butene-1 of 97.2:2.35 is continuously supplied to the reactor so as to maintain a constant pressure of 5 to 1 r/-. The process was completed in 2 hours at a temperature of 70°C.

The yield of the obtained ultra-high molecular weight ethylene-butene-1 copolymer powder was 160r'? :"The intrinsic viscosity [η(decalin: 135° C.)] was 8.2 dj/g, and the butene-1 content as measured by an infrared spectrophotometer was 1.5 per 1000 carbon atoms.

Preparation of stretched and oriented ultra-high molecular weight ethylene/butene-1 copolymer> 20 parts by weight of the ultra-high molecular weight ethylene/butene-1 copolymer powder obtained by the above polymerization and paraffin wax (melting point = 69°C, molecular weight =490>80 parts by weight was melt-spun under the following conditions.

3.5- as a process stabilizer to 100 parts by weight of the mixture.
Di-tert-butyl-4-hydroxytoluene 0
．． The mixture containing 1 part by weight was then melt-kneaded using a screw extruder (screw diameter = 25 mm, L/D = 25, manufactured by Thermoplastics) at a set temperature of 190°C. Subsequently, the mixed melt was melt-spun through a spinning guide with an orifice diameter of 2 mm attached to the extruder, and the extruded melt was taken out at a draft ratio of 36 times through an air gap of 180 mm, and cooled in air. It was solidified to obtain undrawn fibers. Furthermore, the undrawn fibers were drawn under the following conditions.

Two-stage stretching was performed using a Godetstrol made by Ohdai. At this time, the heat medium in the first drawing tank is n-decane, and the temperature is 1
The heating medium in the second drawing tank was triethylene glycol, and the temperature was 145°C. The effective length of the paddles was 50 mm each.

During stretching, the rotational speed of the first godet roll is set to 0.
By changing the rotational speed of the third godet roll to 5 m/min, oriented fibers with a desired drawing ratio were obtained. The rotational speed of the second godet roll was appropriately selected within a range that allowed stable stretching. Almost all of the initially mixed paraffin wax was extracted into n-decane during stretching. Thereafter, the oriented fibers were washed with water, dried under reduced pressure at room temperature overnight, and then subjected to measurement of various physical properties. The stretching ratio was calculated from the rotational speed ratio of the first godet roll and the third godet roll.

Measurement of Tensile Properties> The elastic modulus and tensile strength were measured at room temperature (23° C.) using a DO3-50M tensile tester manufactured by Shimadzu Corporation.

At this time, the sample length between the clamps was 100 nun, and the tensile rate was 100 m/min (100%/min strain rate).1 The elastic modulus was calculated using the slope of the tangent at the initial elastic modulus. The fiber cross-sectional area required for calculation was calculated from the weight, assuming the density as 0.960 g/CC.

Tensile modulus and strength retention after heat history The heat history test was conducted by leaving the material in a gear oven (manufactured by Perfect Oven Nitabai Seisakusho).

The sample had a length of about 3 m, and was folded over a stainless steel frame equipped with a plurality of pulleys at both ends to fix both ends of the sample. At this time, both ends of the sample were fixed to the extent that the sample did not sag, and no tension was actively applied to the sample. The tensile properties after the thermal history were measured based on the description of the measurement of the tensile properties described above.

Measurement of creep resistance> Creep resistance was measured using a thermal stress strain measuring instrument [TMA/5SI
Using O (manufactured by Seiko Electronics Co., Ltd.), the sample length was 1 cm.
The test was carried out under accelerated conditions at an ambient temperature of 70° C. and a weight equivalent to 30% of the breaking load at room temperature. The following two values were determined to quantitatively evaluate the amount of creep. In other words, the creep elongation (%) after 90 seconds after applying a load to the sample
) The value of CR9° and the value of the average creep rate (sec-1) ε after 90 seconds and 180 seconds have elapsed.

Table 1 shows the tensile properties of the multifilament obtained by bundling a plurality of drawn and oriented fibers.

The original crystal melting peak of ultra-high molecular weight ethylene-butene-1 copolymer drawn filament (Sample-1) is 126.7
℃, the ratio of T11 to the total crystal melting peak area is 33
．． It was 8%. Also, the creep resistance is CR9o=3.1
%, ε=3.03X10sec”.Furthermore, 1
The elastic modulus retention after 55 minutes of thermal history at 70"C is 102.
2%, the strength retention rate was 102.5%, and no deterioration in performance due to thermal history was observed.

Also, the amount of work required to break the drawn filament is 10.
3kg-m/g, density is 0.9731r/-, dielectric constant is 2.2, dielectric loss tangent is 0.024%, impulse voltage breakdown value is 180Kv/1II11
And ivy.

Polymerization of ultra-high molecular weight ethylene/octene-1 copolymer in 11 plates> Slurry polymerization of ethylene was carried out using a Ziegler catalyst and n-decane 1j as a polymerization solvent.

At this time, 125 ml of octene-1 as a comonomer and 40 N cal of hydrogen for molecular weight adjustment were added all at once before starting the polymerization to start the polymerization. Ethylene gas was continuously supplied so that the reactor pressure was maintained at a constant pressure of 5 kg/aJ, and the polymerization was completed at 70° C. for 2 hours.

The yield of the obtained ultra-high molecular weight ethylene/octene-1 copolymer powder was 178 g, and its intrinsic viscosity [η] (decalin,
135°C) was 10.66 dJ/g, and the octene-1 comonomer content by infrared spectrophotometer was 0.5 per 1000 carbon atoms.

Preparation of drawn and oriented ultra-high molecular weight ethylene/octene-1 copolymer and its physical properties> A drawn and oriented fiber was prepared by the method described in Reference Example 1. Table 2 shows the tensile properties of the multifilament obtained by bundling a plurality of drawn and oriented fibers.

The original crystal melting peak of the ultra-high molecular weight ethylene/octene-1 copolymer drawn filament (Sample-2) was 132.
Tp and Tpl relative to total crystal melting peak area at 1°C
The percentages were 97.7% and 5.0%, respectively.

The creep resistance of sample-2 is CR90=2, 0%,
ε=9.50×10 sec. Also, 17
The elastic modulus retention after 15 minutes of thermal history at 0°C was 108.
2%, and the strength retention rate was 102.1%. Furthermore, the amount of work required to fracture sample-2 is 10.1 kz・m/
g, the density is 0.971 g/-, and the dielectric constant is 2
．． 2, the dielectric loss tangent was 0.031%, and the impulse voltage breakdown value was 1.85 KV/mm.

Reference Example 3 Ultra-high molecular weight polyethylene (homopolymer) powder (intrinsic viscosity [η] = 7.42 dJ /+r, Decalin, 13
5°C): 20 parts by weight and paraffin wax (melting point -
69°C, molecular weight -490): A mixture of 80 parts by weight was melt-spun and drawn by the method of Reference Example 1 to obtain draw-oriented fibers. Table 3 shows the tensile properties of the multifilament obtained by bundling a plurality of drawn and oriented fibers.

Ultra-high molecular weight polyethylene drawn filament (Sample-3)
The original crystal melting peak was 135.1°C, and the ratio of Tp to the total crystal melting peak area was 8.8%. Similarly, the high temperature side peak Tp1 with respect to the total crystal melting peak area
The proportion was less than 1%. Creep resistance is CR9o=
11,9%, ε-1,07xlO-3Sec-'. In addition, the elastic modulus retention rate after heat history at 170°C for 15 minutes was 80.4%, and the strength retention rate was 78.2%. Furthermore, the amount of work required to break sample-3 is 6.8
kg-m/g, the density is 0.985 t/self,
The dielectric constant is 2.3, the dielectric loss tangent is 0.030%, and the impulse voltage breakdown value is 182 K V / 11 m
Met.

When we actually cleaned between the teeth using the filament prepared in Reference Example 1, we found that the filament was very strong and the monofilament did not break even after cleaning all the spaces between teeth during the day. There were very few of them, and they completely retained their functionality.

Furthermore, when using this filament, the filament was much less likely to get caught on the teeth than conventional filaments, providing an excellent feeling of use.

When we actually cleaned between the teeth using the filament prepared in Reference Example 2, we found that the filament was very strong and the monofilament did not break even after cleaning all the spaces between teeth during the day. There were very few of them, and they completely retained their functionality.

Furthermore, when using this filament, the filament was much less likely to get caught on the teeth than conventional filaments, providing an excellent feeling of use.

When we actually cleaned between the teeth using the filament prepared in Shakutate Goyu Reference Example 3, we found that the filament was very strong and the monofilament did not break even after cleaning all the spaces between teeth during the day. There were very few of them, and they completely retained their functionality.

Furthermore, when using this filament, the filament was much less likely to get caught on the teeth than conventional filaments, providing an excellent feeling of use.

Agent: Patent Attorney: Shunbetsu Suzuki

Claims (1)

[Scope of Claims] 1) Dental floss made of a drawn multifilament of ultra-high molecular weight polyolefin having an intrinsic viscosity [η] of at least 5 dl/g. 2) Ultra-high molecular weight ethylene α- having an intrinsic viscosity [η] of at least 5 dl/g and containing an average of 0.1 to 20 α-olefins having 3 or more carbon atoms per 1000 carbon atoms. Dental floss made of drawn multifilaments of olefin copolymer. 3) α-olefin is butene-1, 4-methylpentene-1, hexene-1, octene-1 or decene-1
The dental floss according to claim 2. 4) The dental floss according to claim 2, wherein the content of α-olefin is on average 0.5 to 10 per 1000 carbon atoms.