JPH06168625A - Application of cyclopentene polymer - Google Patents

Abstract

PURPOSE:To provide an electric insulating material having performance appropriate for medical equipment, of which quality is not changed by the contact with the drug for a long time and which does not change the quality of the medicine, and for electronic parts processing equipment, which is hard to be influenced by the treatment liquid and appropriate for the high temperature processing, and for a high frequency circuit board having a low dielectric constant and a low dielectric tangent. CONSTITUTION:Cyclopentene monomer such as 4,7-methano3a,4,5,6,7,7a- hexahydro-1H-indene at 35 to 100wt.% and alpha-olefine monomer such as ethylene at 65 to 0wt.% are (co)polymerized to form a cyclopenten polymer. The cyclopentene polymer having the limiting viscosity [eta] at 0.1 to 10dl>=/g measured in toluene at 25 deg.C is used for medical equipment, electronic parts processing equipment or electric insulating material. The excellent performance is showed in each application.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medical device, a device for processing electronic parts, or an electrically insulating material made of a cyclopentene polymer.

[0002]

Cyclopentene polymers have a melting point of 39.
Although it is a resin as high as 5 ° C, a copolymer of ethylene and cyclopentene becomes an amorphous resin when the copolymerization ratio of cyclopentene is about 10% by weight or more, and has a high glass transition temperature.
It is known that it has excellent chemical resistance and can be used as an optical material (Bull. Soc. Chi.
m. Belg. vol. 99, No. 2, 10
3-111, 1990; Makromol. Ch
em. , Macromol. symp. 47,
83-93, 1991; etc.). However, there has not been known any other polymer obtained by polymerizing a monomer having a cyclopentene ring structure, or their electrical properties and low elution properties.

[0003]

The present inventors have earnestly studied for the purpose of developing a resin having excellent heat resistance, optical characteristics, electrical characteristics, chemical resistance and the like, and as a result, polymerized a cyclopentene monomer. , Or a cyclopentene-based polymer obtained by copolymerizing a cyclopentene-based monomer and an α-olefin-based monomer, has excellent transparency, photodegradation resistance, low birefringence, and chemical resistance, and medical equipment and electronic component processing equipment. It has been found that it can be used as an electric insulating material, or has completed the present invention.

[0004]

Thus, according to the present invention, 35 to 100% by weight of cyclopentene-based monomer and α
-It is formed by (co) polymerizing 65 to 0% by weight of an olefinic monomer, and has an intrinsic viscosity [η] measured in toluene at 25 ° C.
There is provided a medical device, a device for processing electronic parts, and an electrically insulating material, which are made of a cyclopentene-based polymer having 0.1 to 10 dl / g.

(Cyclopentene Monomer) The cyclopentene monomer used in the present invention is a hydrocarbon having a cyclopentene ring represented by the following general formula 1, its halogen, hydroxyl group, ester group, alkoxy group, cyano group,
It is a substituted polar group such as an amide group, an imide group, and a silyl group.

General formula 1:

[Chemical 1]

R ^{1 to} R ⁸ in the general formula 1 are hydrogen atom, hydrocarbon group, halogen, hydroxyl group, ester group, alkoxy group, cyano group, amide group, imide group,
It represents a polar group such as a silyl group, or a hydrocarbon group substituted by these polar groups. R ³ or R ⁴ and R ⁷ or R ⁸ , R ⁵ or R ⁶ and R ⁷ or R ⁸ may form part of another ring structure. Since the cyclopentene-based polymer is preferably not crosslinked, the cyclopentene-based monomer is preferably a cyclopentene-based polymer having no unsaturated bond involved in addition polymerization other than one unsaturated bond in the cyclopentene ring structure.

Examples of such cyclopentene-based monomers include cyclopentene, 3-methyl-cyclopentene, 4-ethyl-cyclopentene, 3,4-dimethyl-cyclopentene, 4-methoxycarbonyl-cyclopentene, 4-phenyl-cyclopentene and the like. Monocyclic monomer; 4,7-methano-3a, 5,6,7a-tetrahydro-1H-indene, 4-methyl-4,7-methano-3a, 5,6,7a-tetrahydro-1H-indene, 4, 7-methano-3a, 4,5,6,7,7a-hexahydro-1H-indene, 4,9,5,8-dimethano-3a, 4a, 6,7,8a, 9a-hexahydro-
Examples are polycyclic monomers such as 1H-benzoindene; and the like. To obtain a resin having good heat resistance, it is preferable to use many polycyclic monomers.

(Comonomer) In the present invention, a cyclopentene-based monomer and an α-olefin-based monomer may be copolymerized. The copolymerization ratio is 35 to 100% by weight, preferably 50 to 100% by weight, and 65 to 0% by weight, and preferably 50 to 0% by weight, of the α-olefin type monomer. When the amount of the α-olefin-based monomer is too much, the heat resistance becomes poor.

As the α-olefin type monomer used in the present invention, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 3
-Methyl-1-butene and the like are exemplified.

(Third Component Comonomer) A third component comonomer may be used as long as the object of the present invention is not impaired. Examples of the third component comonomer include isobutene, styrene, α-methylstyrene, norbornene, dicyclopentadiene and the like.

(Polymerization catalyst) The polymerization catalyst used for (co) polymerization of the monomer used in the present invention is disclosed in JP-A-61-2212.
No. 06, No. 2-173112, No. 3
-45612, Japanese Patent Publication No. 3-234716, etc., and is composed of a transition metal compound and an organoaluminum oxy compound.

The transition metal compound used in the present invention is, for example, a polydentate compound in which at least two cycloalkadienyl groups or substituted products thereof are bound via a hydrocarbon group, a silylene group or a substituted silylene group. As a ligand, and preferably a bidentate compound bonded via a silylene group or a substituted silylene group as a ligand. Transition metals include zirconium, titanium,
Hafnium, chromium and vanadium are preferable, and zirconium and hafnium are particularly preferable. Specific examples of the transition metal compound used in the present invention when the transition metal is zirconium include dimethylsilylenebis (siluropentadienyl) zirconium monochloride monohydride,
Dimethylsilylenebis (cyclopentadienyl) dimethylzirconium, silylenebis (cyclopentadienyl) zirconium dichloride, dimethylsilylenebis (indenyl) ethoxyzirconium chloride, dimethylsilylenebis (4,5,6,7-tetrahydro-1-
Examples thereof include indenyl) ethyl zirconium ethoxide, dimethylsilylene bis (5-methyl-1-indenyl) zirconium dichloride, and dimethylsilylene bis (fluorenyl) zirconium dichloride.

Examples of the organoaluminum oxy compound used in the present invention include known aluminoxanes. The method for producing aluminoxane is not particularly limited, and for example, an organoaluminum compound is added to and reacted with a hydrocarbon medium suspension of a compound containing adsorbed water or a salt containing water of crystallization to obtain a hydrocarbon solution. The method of collecting is mentioned. Examples of compounds containing adsorbed water or salts containing water of crystallization include magnesium chloride hydrate, copper sulfate hydrate, aluminum sulfate hydrate, nickel sulfate hydrate, and ceric chloride hydrate. To be Examples of the hydrocarbon medium include aliphatic hydrocarbons such as butane, isobutane, and hexane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene. Examples of the organoaluminum compound include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisopropylaluminum, and tricyclohexylaluminum; dialkylaluminum halides such as dimethylaluminum chloride and diethylaluminum bromide; dialkyls such as diethylaluminum hydride and diisobutylaluminum hydride. Aluminum hydride; Dialkyl aluminum alkoxides such as dimethyl aluminum methoxide and diethyl aluminum ethoxide; Dialkyl aluminum aryloxides such as diethyl aluminum phenoxide;
Trialkylaluminum is preferred.

(Polymerization Conditions) The (co) polymerization conditions of the monomers used in the present invention are not particularly limited as long as the polymerization is carried out, and for example, the method known in the above-mentioned publication may be used. For example, in a hydrocarbon solvent, usually -50 to 150 ° C, preferably-
It is carried out at 30 to 100 ° C. The catalyst concentration in the polymerization reaction system is such that the transition metal compound has a concentration of transition metal atoms of usually 10 ⁻⁸ to 10 ⁻² gram atom / l, preferably 10 ⁻⁷ to
10 ^-3 gram atom / l, organoaluminum oxy compound is usually 10 ^-4 to 10 as the concentration of aluminum atom.
^-1 gram atom / l, preferably 10 ^{-3 to} 5 x 10 ^-2 gram atom / l. The amount ratio of aluminum atoms to transition metal atoms in the polymerization reaction system is usually 4 to 1
It is preferably 0 ⁷ , especially 10 to 10 ⁶ . The molecular weight of the copolymer can be controlled by methods such as blowing hydrogen into the polymerization reaction system, changing the polymerization temperature, and diluting the polymerization reaction system with a solvent.

(Polymer) The cyclopentene polymer used in the present invention is obtained by (co) polymerizing 35 to 100% by weight of a cyclopentene monomer and 65 to 0% by weight of an α-olefin monomer in toluene at 25 ° C. It has an intrinsic viscosity [η] of 0.1 to 10 dl / g.

When the cyclopentene-based monomer is cyclopentene and the comonomer is ethylene only, the glass transition temperature (hereinafter referred to as Tg) at 50% by weight of cyclopentene is about 110 ° C. and the Tg at 35% by weight is about 70 ° C. As the copolymerization ratio of
Tg rises.

The cyclopentene-based monomer is 4,7-methano-3a, 4,5,6,7,7a-hexahydro-1H.
The same is true when the indene and the comonomer are only ethylene, and the Tg at 50% by weight of cyclopentene is about 160 ° C, and the Tg at 35% by weight is about 130 ° C.

(Additive) If desired, various additives may be added to the polymer of the present invention. Examples of the additives used include phenol-based and phosphorus-based antioxidants, antistatic agents, ultraviolet absorbers, rubber polymers, petroleum resins, and heterogeneous thermoplastic resins. For the purpose of improving moldability and physical properties, for example, fibrous fillers such as glass fiber and carbon fiber; fine particle fillers such as silica, alumina, talc, aluminum hydroxide and calcium carbonate; tetrakis [2- (3,5-di-t-butyl-4-hydroxyphenyl) ethylpropionate] methane, 2,6-di-t-butyl-4-methylphenol and other antioxidants; Stabilizers, ultraviolet absorbers, antistatic agents, lubricants, flame retardants, pigments, dyes, antiblocking agents and the like may be added. In general, in order to prevent elution from the polymer, it is preferable that these additives have a higher molecular weight, and a smaller addition amount is more preferable.

When the sheet is formed by the solution spraying method,
A leveling agent may be added to reduce the surface roughness. As the leveling agent, for example, a fluorine-based nonionic surfactant, a special acrylic resin-based leveling agent, a silicone-based leveling agent, or the like can be used as a coating leveling agent, and among them, those having good compatibility with a solvent are preferable.

When an additive is added to the polymer of the present invention, it is added within the range according to the purpose. For example, when an additive is added, the transparency generally decreases, but when molding into a chemical container, it is necessary to have a transparency that allows the amount and state of the contents to be confirmed, and therefore the required light transmission. As for the rate, a molded plate with a thickness of 1.2 mm is used, and the wavelength range is 400
It is usually 40% or more, preferably 50% or more, more preferably 60% or more when measured in the range of up to 700 nm.
Similarly, the light transmittance when used as an optical material is
Measured at a wavelength of 400 to 830 nm, usually 80% or more,
It is preferably at least 85%, more preferably at least 88%.

Additives also affect the electrical properties. When used as an electrically insulating material, the volume resistivity value is 10 ¹⁶ Ωcm or more, preferably 5 × 10 ¹⁶ Ωcm or more,
The dielectric constant is 3 or less, preferably 2.5 or less at any frequency of 10 ² Hz, 10 ⁶ Hz, or 10 ⁹ Hz, and the dielectric loss tangent is any of 10 ² Hz, 10 ⁶ Hz, or 10 ⁹ Hz. 10 ^-3 or less, preferably 7 × 10 ^-4 or less.

(Molding) The method for molding the polymer of the present invention or the composition containing the additive is not particularly limited. The molding method may be selected according to the melting point and Tg of the polymer, the purpose of use, the shape of use, and the like. For example, an injection molding method, a press molding method, a solution casting method, a blow molding method, an extrusion molding method or the like can be used.

(Medical device) The medical device of the present invention comprises the cycloentene polymer obtained as described above.
The cyclopentene-based polymer used in the present invention is a drug, particularly alcohols, amines, esters, amides,
Since it absorbs little chemicals with polar groups such as ethers, carboxylic acids, amino acids, etc., and the organic substances contained as impurities in the resin rarely exude, so it should be altered even when it comes into contact with chemicals. There is no. further,
Pore volume 0.5 cm ³ / g or more, preferably 0.7 cm ³
/ G or more, and preferably a specific surface area of 250 m ² / g or more is treated with an adsorbent made of magnesia, activated alumina, synthetic zeolite, or the like, or the resin solution is repeatedly washed with acidic water and pure water to form a polymerization catalyst. Reduce the amount of residual transition metal atoms derived from
Since it can be set to m or less, it can be used as a medical device.

The medical device of the present invention is, for example, a liquid or powder such as a liquid medicine container for injection, an ampoule, a prefilled syringe, an infusion bag, a solid medicine container, an eye drop container, an instillation container, or the like. Chemical containers; Food containers; Sampling test tubes for blood tests, blood collection tubes, sample containers such as sample containers; Medical devices such as syringes;
Sterile containers for medical instruments such as scalpels, forceps, gauze and contact lenses; experimental and analytical instruments such as beakers, petri dishes, flasks, test tubes, centrifuge tubes; medical optical components such as plastic lenses for medical examinations; medical infusions Piping materials such as tubes, pipes, joints, valves; artificial dentures, artificial hearts, artificial roots and other artificial organs and parts thereof;
Are exemplified. In particular, in the case of medicine bottles, prefilled syringes, sealed medicine bags, ampoules, vials, eye drop containers, etc., which store medicines, especially liquid medicines for a long period of time, compared to conventional resin ones, transparency, In addition to physical properties, there are no impurities that elute from the resin, it has excellent chemical resistance, and since it does not adsorb chemicals, it has the favorable property that the quality of chemicals is small.

The electronic component processing equipment of the present invention comprises the cyclopentene polymer obtained as described above. Cyclopentene-based polymers, particularly those having a transition metal residue of 1 ppm or less by the above-mentioned method, have substantially no impurities eluted from the resin, and have excellent physical properties such as heat resistance, and also can be used for electronic parts treatment. Since it has resistance to many chemicals used for use, especially most of strong acids except sulfuric acid, it has preferable properties as a device for processing electronic parts.

The electronic component processing equipment is (A) IC, L
Semiconductors such as SI, hybrid ICs, liquid crystal display elements,
Equipment that contacts electronic parts such as light-emitting diodes, (B)
Wafers, liquid crystal substrates, equipment that comes into contact with manufacturing intermediates such as those having a transparent electrode layer or protective layer laminated thereon, and (C) chemical liquids or super liquids used in the processing of manufacturing intermediates in the manufacturing process of electronic components. Equipment that comes into contact with processing liquid such as pure water. Examples of (A) the equipment that comes into contact with the electronic component and (B) the equipment that comes into contact with the intermediate for manufacturing the electronic component include, for example, a tank,
Containers for treating and transferring trays, carriers, cases, etc .; carrier tapes, protective materials such as separation films; and the like. (C) Examples of equipment that comes into contact with the treatment liquid include pipes, tubes, valves, sippers, flow meters, filters, pumps, and other pipes; sampling containers, resist containers, developer containers, stripping liquid containers, cleaning liquid containers, Liquid containers such as bottles, ampoules and bags; and the like.

(Electrical Insulation Material) The electrical insulation material of the present invention comprises the cyclopentene polymer obtained as described above. Cyclopentene-based polymers have excellent electrical insulation properties, for example, coating materials for electric wires and cables,
General insulation materials for consumer and industrial electronic equipment, office automation equipment such as copiers, computers and printers, and measuring instruments;
Circuit boards such as rigid printed boards, flexible printed boards, and multilayer printed wiring boards, especially high-frequency circuit boards for satellite communication devices that require high-frequency characteristics; surface heat generation of liquid crystal boards, optical memories, defrosters of automobiles and aircraft, etc. Substrate of transparent conductive film such as body; semiconductor encapsulant and parts such as transistor, IC, LSI, LED;
Encapsulation materials for electric and electronic parts such as motors, contactors, switches and sensors; body materials for TVs and video cameras; parabolic antennas, flat antennas, etc.
It can be preferably used as a structural member of a radar dome.

[0029]

EXAMPLES The present invention will be described more specifically below with reference to Reference Examples, Examples, and Comparative Examples. Note that Tg is D
By the SC method, the light transmittance was measured with a spectrophotometer at wavelengths of 400 to 700 nm and 830 nm. In the wavelength range of 400 to 700 nm, the wavelength of 4
The light transmittance at 00 nm is the lowest, and only that value is shown.

Reference Example 1 After a glass reaction vessel provided with a blowing tube was replaced with nitrogen, 5.2 parts by weight of a toluene solution of polymethylaluminoxane (manufactured by Tosoh Akzo Co., aluminum concentration 7.6%) and zirconocene were added. 4.3% by weight of a 1% toluene solution of dichloride was charged, and the mixture was cooled to 0 ° C. with stirring. After 3 minutes, 100 parts by weight of a 10% toluene solution of cyclopentene was added, and immediately, blowing of ethylene gas diluted with nitrogen to a concentration of 10% into the reaction solution was started, and 0.
It was distributed at a rate of 3 liters. After reacting for 5 hours as it was, 200 parts by weight of toluene was added to the reaction solution to dilute it, and then immediately, the reaction solution was poured into 1000 parts by weight of strongly stirred methanol, and the precipitated polymer was collected by filtration. The polymer was washed twice with 100 parts by weight of methanol to which 5% of hydrochloric acid was added, and then washed with 100 parts by weight of methanol three times. Further, it was dried under a reduced pressure of 1 mmHg for 24 hours to obtain 8.7 parts by weight of a colorless resin. 25 ° C,
The intrinsic viscosity measured in toluene was 0.43 dl / g. The Tg was 128 ° C.

Example 1 The resin obtained in Reference Example 1 was press-molded at 180 ° C. to obtain a dish-shaped transparent container having an upper diameter of 80 mm, a bottom diameter of 60 mm, a height of 30 mm and an average thickness of 3 mm, and 40 mm × 30 mm ×
2.0 mm test piece, thickness 1.2 mm, diameter 1
A 2.5 cm rolled plate was prepared.

The light transmittance of the test piece was measured to be 88.0% at a wavelength of 400 nm and 89.8% at a wavelength of 830 nm.
%Met. The turbidity was measured and found to be 0.08%. Because of this and the high Tg, it can be used as an optical material.

2% by weight of agar was added to LB medium (1% by weight of bactotryptone, 0.5% by weight of yeast extract, 1% by weight of NaCl, 0.1% by weight of glucose was adjusted to pH 7.5). , Sterilize it by steam sterilization at 121 ℃ for 30 minutes to gel it,
1 was placed in an aseptically molded container, left at room temperature for 6 hours, capped with aluminum foil, and irradiated with 25 kGy of γ rays for sterilization. After the treatment, the temperature was kept at 37 ° C for 3 days, but no fungal growth was observed. Moreover, the appearance of the transparent container after the treatment was good, and no cloudiness, cracking, or deformation was visually confirmed.

The test piece was immersed in a sodium carbonate aqueous solution having a pH of 9, a hydrochloric acid having a pH of 4, and ethanol for 48 hours, and then the appearance was observed, but no change was observed, and neither turbidity nor light transmittance was changed.

20 g of this test piece was ultrasonically washed in distilled water for 20 minutes and then dried at 40 ° C. for 10 hours. The test piece was placed in a hard glass flask, and 200 g of distilled water was added. A lid made of hard glass was placed and the mixture was allowed to stand at 50 ° C. for 24 hours to collect distilled water. As a control, 200 g of distilled water was placed in a hard glass flask, a hard glass lid was placed, and the same was left at 50 ° C. for 24 hours.

The elution amount from the test piece was obtained from the difference in the analysis results by the atomic absorption method of these two kinds of distilled water, the ion chromatography, the combustion-non-dispersion infrared gas analysis method, etc., and the zirconium atom elution amount was obtained. Is 0.01 ppm
Below the (detection limit), the elution amount of aluminum atoms is 0.01
It was below ppm (detection limit).

The test piece was subjected to an eluate test according to the 12th revision of the Japanese Pharmacopoeia “Plastic Test Method for Infusion Solution”. Effervescence disappeared within 3 minutes, pH difference was -0.03, ultraviolet absorption was 0.004, and potassium permanganate reducing substance was 0.18 ml. From these facts, it was found that they can be used as medical equipment and electronic component processing equipment.

The volume resistivity value of this resin measured using the produced disc was 5 × 10 ¹⁶ Ωcm or more, and the dielectric constant was ² at any frequency of 10 ² Hz, 10 ⁶ Hz, or 10 ⁹ Hz. .40, dielectric loss tangent is 10 ² Hz, 10 ⁶ H
5 × 10 ⁻⁴ at any frequency of z and 10 ⁹ Hz
Met. From this, it was found that it can be used as an electrically insulating material.

Reference Example 2 4,7-Methano-3a, 4,5,6,7,7a-instead of 100 parts by weight of a 10% toluene solution of cyclopentene.
Hexahydro-1H-indene 10% Toluene Solution 1
A colorless resin (6.3 parts by weight) was obtained in the same manner as in Reference Example 1, except that the amount of ethylene gas diluted with nitrogen was 0.21 l / min. The intrinsic viscosity measured in toluene at 25 ° C. is 0.52 dl / g and T
The g was 145 ° C.

Example 2 The resin obtained in Reference Example 2 was press-molded at 200 ° C. to prepare a transparent dish-shaped container, a test piece and a disc similar to those in Example 1.

The light transmittance of the test piece was measured and found to be 88.1% at a wavelength of 400 nm and 90.4 at a wavelength of 830 nm.
%Met. Also, when the turbidity was measured, it was 0.10%
Met.

80 ml of the same LB medium as in Example 1 and one piece of a test piece were placed in a molded container, capped with aluminum foil, and steam sterilized at 120 ° C. for 30 minutes.

After the treatment, the temperature was kept at 37 ° C. for 3 days, but no fungal growth was observed. The appearance of the transparent container after the treatment was good, and no turbidity, cracking, or deformation due to heat was visually confirmed.

The turbidity measured after removing the LB medium solidified by agar from the test piece taken out from the container was 0.
15%, and the light transmittance is 89.8 at a wavelength of 830 nm.
%Met.

Further, the test piece was immersed in a sodium carbonate aqueous solution having a pH of 9, a hydrochloric acid having a pH of 4 and ethanol for 48 hours and then the appearance was observed, but no change was observed, and neither turbidity nor light transmittance was observed.

When the elution amount of metal atoms was measured with distilled water in the same manner as in Example 1, the elution amount of zirconium atoms was 0.01 ppm or less, and the elution amount of aluminum atoms was 0.01 ppm or less.

When the same eluate test as in Example 1 was conducted, foaming disappeared within 3 minutes, the pH difference was -0.01,
Ultraviolet absorption was 0.003 and potassium permanganate reducing substance was 0.12 ml.

Further, the volume resistivity of this resin measured using the produced disk was 5 × 10 ¹⁶ Ωcm or more, and the dielectric constant was ² at any frequency of 10 ² Hz, 10 ⁶ Hz, or 10 ⁹ Hz. .35, dielectric loss tangent is 10 ² Hz, 10 ⁶ H
5 × 10 ⁻⁴ at any frequency of z and 10 ⁹ Hz
Met. From this, it was found that it can be used as an electrically insulating material.

[0049]

Industrial Applicability The medical device of the present invention does not deteriorate even if it is in contact with a drug for a long time, and does not deteriorate the drug. Further, the electronic component processing equipment of the present invention is not easily affected by the processing station and is also suitable for high temperature processing and the like. Furthermore, the electric insulating material of the present invention has a low dielectric constant and a low dielectric loss tangent, and has performance suitable for a high frequency circuit board and the like.

Claims (1)

[Claims] 1. A cyclopentene-based monomer 35 to 100
From a cyclopentene-based polymer having an intrinsic viscosity [η] of 0.1 to 10 dl / g measured in toluene at 25 ° C., which is (co) polymerized with 65 to 0% by weight of α-olefin monomer. Comprising medical equipment, electronic component processing equipment, or electrical insulation material.