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CA1068034A - Production of diffusing discs using sheets of glass fiber-filled thermoplastics - Google Patents

Production of diffusing discs using sheets of glass fiber-filled thermoplastics

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Publication number
CA1068034A
CA1068034A CA255,344A CA255344A CA1068034A CA 1068034 A CA1068034 A CA 1068034A CA 255344 A CA255344 A CA 255344A CA 1068034 A CA1068034 A CA 1068034A
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Prior art keywords
molecular weight
weight
glass fibers
disc
diffusing
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CA255,344A
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French (fr)
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Joachim Wank
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Bayer AG
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Bayer AG
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/06Fibrous reinforcements only
    • B29C70/10Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
    • B29C70/12Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of short length, e.g. in the form of a mat
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29DPRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00Producing optical elements, e.g. lenses or prisms
    • B29D11/00605Production of reflex reflectors

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Textile Engineering (AREA)
  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Ophthalmology & Optometry (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Reinforced Plastic Materials (AREA)
  • Pens And Brushes (AREA)
  • Braking Arrangements (AREA)
  • Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Abstract

Abstract of the Disclosure Diffusing discs are produced by incorporating glass fibers into thin sheets of thermoplastic resin. The glass fibers are incorporated into the resin by conventional methods and formed into sheets according to well known thermoplastic forming processes. The sheets so produced display the ability to act as diffusing discs without any special surface preparation.

Description

Mo-1629-P
LeA 16,536 :~068034 PRODUCTION OF DIFFUSING DISCS
USING SHEETS OF GLASS FIBER-FILLED THERMOPLASTICS

Field of the Invention The term "diffusing discs" means sheet-like or shaped structures with wall thicknesses of from 0.005 to 20 mm, which deflect a ray of light vertically on the surface of the ~ ;
diffusing discs from its direction as the ray passes through or emerges from the discs.

Background of the Invention Sheets of glass fiber-filled thermoplastics are known in principle. (See, for example, West German Offenlegungsschrift (German Published Specification) 2,437,508). They can be produced by mixing glass fibers with a plastic melt and pressing ;
this plastic melt containing glass fibers out through a nozzle.
Very diverse transparent polymers are suitable as thermoplastics for this purpose. Suitable ~lass fibers are all the commercially available sorts and types of glass fibers, that is to say chopped glass fibers (long glass fibers and short glass fibers), rovings or staple fibers, on condition that they are finished with sizes suitable for the particular polymer used. Whether or not the glass filaments are bundled into fibers or the fibers in turn are bundled into yarns, cables or hanks or, for example, are woyen into mats, the length of the glass filaments should be between 60 mm and 6 mm in the case of long glass and the maximum length should be between 5 mm (5,000 ~m) and 0.05 mm (50 ~m) in the case of short glass. Two types of glass fiber are particularly pre~ferred:

LeA 16,536 10~8~3~

I. Long glass fibers with an average fiber length of 6,000 ~m, a diameter of 15 ~m and a powder content (< 50 ~m) of about 1% by weight and II. Ground shoxt glass fibers with an average fiber length of 230 ~m, a diameter of 13 ~m and a powder content ( < 50 ~m) of 5~ by weight.

Alkali-free aluminum-borosilicate glass ("E-glass") -or alkali-containing "C-glass" can be used as the glass material. Suitable sizes which can be used are those known -from the literature; the water size known for short glass fibers has proved particularly useful for polycarbonate compositions. (Compare West German Auslegeschrift (German Published Specification) l 201 991~

With regard to the industrial use of sheets of glass fiber-filled thermoplastics, the sole recommendation hitherto has been to use these as electrical insulating materials.

Diffusing discs are used, for example, for signal elements in single-and multi-function monitoring instruments or flow sheets panels. Diffusing discs should be of uniform brightness over their entire area. They can be colored in different colors or printed with transparent colors. Diffusing discs have hitherto been produced from etched glass or from delustered plastic sheets. Delustered plastic sheets are preferred to etched glass because of greater safety, simpler production of pieces cut to size and better printability. -~

LeA 16,536 -2-.
- ~ ~

9.~ 3034 However, the delustering of such plastic sheets which are suitable for the production of diffusing discs must be particularly good. Unevenness in delustering leads to variations in the brightness in transmitted light. However, the delustering of the plastic sheet, which generally has a peak-to-valley height of between 0.2 ~m and 2 ~m, is very sensitive to mechanical damage, which can arise during the production and during the further processing of the sheet.
These disadvantages could be avoided if the light is diffused not at the delustered surface of the plastic sheet but inside the plastic sheet, that is to say when sheets are used which, instead of or in addition to being delustered, contain, for example, pigments. Using the diffusing pigments known hither-to for examples barium sulphate, titanium dioxide, carbon black or silicon dioxide, it is possible to achieve an adequate diffusion effect, for a light transmission of, for example, 30%, only with sheet thicknesses of more than 2 mm and, in general, extensive self-coloring rises which, for example, leads to the back of a sheet printed red-transparent on one side being orange in transmitted light.

Summary of the Invention Surprisingly, it has now been found that sheets of ;
glass fiber-filled thermoplastics already achieve a diffusing effect which is adequate for the production of diffusing discs at a layer thickness of about 30 ~m to 1,000 ~m with a glass fiber content between about 20% by weight and 30% by weight, based on the total weight of the glass fiber-filled thermo-plastic. The diffusing effect of these sheets is independent of the nature of their surfaces; thus, the sheets can be handled, stored, wound up, printed or punched considerably ~ _3_ B LeA 16,536-Ca 8~3~
more easily. The surface of the sheets of glass fiber-filled thermoplastics can also be embossed, grained or provided with other reliefs, without an impairment in the diffusing effect of the sheets having to be accepted.

The subject of the present invention thus relates to a process for the production of diffusing discs comprising forming the discs from about 30 ~m to 1,000 ~m thick sheets of glass fiber-filled thermoplastics selected from the group consisting of a cellulose ester having a (Mw) of about 10,000 ~0 to 1,000,000, a polycarbonate having a molecular weight (Mw) of between about 10,000 and 100,000, a polyaryl-sulphone having a molecular weight (Mw) of between about 1,000 and 200,000, a polyphenylene oxide having a molecular weight (Mw) of about 2,000 to 100,000 and a polyalkylene terephthalate having a molecular weight (Mw) of about 10,000 to ~0,000 with between 20% by weight and 30% by weight, based on the total weight of the glass fiber-filled thermoplastic, of glass fiber selected from the group consisting of glass fibers with an average fiber length of between 60 mm and 6 mm and glass fibers with an average fiber length of between 5 mm and 0.5 mm.

The instant invention also relates to a diffusing disc in which the proportion of light incident on the disc which passes directly through the thickness of the disc is not measurable with a spectrophotometer said disc produced by incorporating about 20 to 30 weight %, based on the total weight of filled thermoplastic, of glass fibers selected from the group consisting of glass fibers with an average fiber length of between 60 mm and 6 mm and glass fibers with an average fiber length of between 5 mm and 0.5 mm into a thermoplastic resin selected from the group consisting of -3a-LeA 16,536-Ca : ; - - ., . . , . . ~ :

:~068~34 a cellulose ester having a molecular weight (Mw) of about 10,000 to 1,000,000 a polycarbonate having a molecular weight (Mw) of between about 10,000 and 100,000, a polyaryl-sulphone having a molecular weight (Mw) of between about -1,000 and 200,000, a polyphenylene oxide having a molecular weight (Mw) of about 2,000 to 100,000 and a polyalkylene terephthalate having a molecular weight (Mw) of about 10,000 to 80,000, forming the resin into a sheet with a thickness of between about 30 and 1,000 ~m and forming said disc from the sheet.

Finally, the instant invention relates to light diffusing apparatuses such as, for example, single- and multi-function monitoring instruments and flow sheet panels incorporating the diffusing discs of the instant invention.

Detail d Description of the Invention In the sense of the invention, polyolefines are polymers of aliphatic unsaturated hydrocarbons, such as, for example, ethylene, propylene, butylene or isobutylene, which are obtained according to customary processes, for example by free-radical polymerization, and must have average weight-average or molecular weights (Mw) (measured by gel chromatographic methods) of between about 1,000 and 3,000,000. 8Oth high-pressure polyolefine and low-pressure polyolefine can be used.

LeA 16,536-Ca ..~
~ 7 The unsaturated hydrocarbons can also be copolymexised with other vinyl monomers, such as, for example, vlnyl acetate, in a known manner.

Cellulose esters in the sense of the invention are obtained according to customary processes by esterification of cellulose with aliphatic monocarboxylic acia anhydrides, preferably acetic anhydride and butyric anhydride or acetic anhydride and propionic anhydride. The hydrolysis to be carried out in the crude solution is so controlled by a slight excess of water that a low hydroxyl content ( 4 to 25) is obtained. The oxidative bleaching of the cellulose ester isolated from the solution must be so carried out that no further oxidizing agent can be detected in the end product;
if necessary, an after-treatment with reducing agents must be carried out.

In order to determine the OH number, the free hydroxyl groups in the cellulose ester are esterified with acetic anhydride in pyridine and the excess anhydride is reacted with water and back-tltrated ~Instruction: C. J. Mahn, L. B.
Genung and R. F. Williams, Analysis of Cellulose Derivatives, Industrial and Engineering Chemistry, Vol. 14, No. 12, 935-940 (1942)].

The vi3cosity of the cellulose esters should be about 0.3 to 0.5 poise, measured as a 20% strength by weight solution in acetone. Cellulose esters which are preferably to be used have an acetic acid content of about 17 to 23% by weight and a butyric acid content of about 45 to 50% by weight in the ~ase of the acetobutyrates and a propionic acid content of about 61 -LeA 16,536 -5-10~:;8034 69% by weight and an acetic acid content of about 2 to 7~ by weight in the case of the acetopropionates. The OH numbers are usually between about 4 and 25. The average weight-averages ~-of the molecular weights Mw must be between about 10,000 and 1,000,000 preferably between about 100,000 and 500,000.

Possible polycarbonates in the sense of the invention are the polycondensation products which are obtainable by ~ -reacting aromatic dihydroxy compounds, especially dihydroxy-diarylalkanes, with phosgene or diesters or carbonic acid and, in addition to the unsubstituted dihydroxydiarylalkanes, those dihydroxydiarylalkanes in which the aryl radicals in the o-position and/or m-position to the hydroxyl group carry methyl groups or halogen atoms are also suitable for this reaction. Branched polycarbonates are also suitable. ~-~

The polycarbonates to be stabilized must be average weight-averages of the molecular weights Mw of between about 10,000 and 100,000, preferably between about 20,000 and 40,000, which are determined by measuring nrel in CH2C12 at 20C and ;
a concentration of 0.5% by weight.

Examples of suitable aromatic dihydroxy compounds are hydroquinone, resorcinol, 4,4' -dihydroxydiphenyl, bis-(hydroxyphenyl)-alkanes, such as, for example, Cl-C8-alkylene-and C2-C8-alkylidene-bisphenols, bis-(hydroxyphenyl)-cyclo-alkanes, such as, for example, C5-C15-cycloalkylene- and C5-C15-cycloalkylidene-bisphenols, bis-(hydroxyphenyl)-sulphides, bis-(hydroxyphenyl) ethers, bis-(hydroxyphenyl) LeA 16,536 -6-, - .:

10~;8034 ketones, bis-(hydroxyphenyl) sulphoxides or bis-(hydroxyphenylJ-sulphones, as well aR ~ bis-(hydroxypheny~)-diisopropyl-benzene and the corresponding nuclear-alkylated and nuclear-halogenated compounds. Polycarbonates based on 2,2-bis- . ~ -(4-hydroxyphenyl)-propane (bisphenol A), 2,2-bis-(4-hydroxy-3,5-dichlorophenyl)-propane (tetrachlorobisphenol A), 2,2-bis-(4-hydroxy-3,5-dibromophenyl)-propane (tetrabromobis-phenol A), 2,2-bis-(4-hydroxy-3,5-dimethylphenyl)-propane (tetramethylbisphenol A), 1,1-bis-(4-hydroxyphenyl)-cyclo-hexane (bisphenol Z) and polycarbonates based on bisphenols with three nuclei, such as ~,~'-bis-(4-hydroxyphenyl)-P-diisopropylbenzene, are preferred. -Further aromatic dihydroxy compounds which are suit-able for the preparation of polycarbonates are described in U. S. Patents 2,970,131, 2,991,273, 2,999,835, 2,999,846, 3,014,891, 3,028,365, 3,062,781, 3,148,172, 3,271,367, 3,271,368 and 3,280,078.

Poly-(2,6-dialkyl-1,4-phenylene oxides) in the sense of the invention are those which have weight-average molecular weights Mw (measured by the light scattering method in chloro-form) of between about 2,000 and 100,000, preferably between about 20,000 and 60,000, and which are obtained according to the known methods by oxidatiYe condensation of 2,6-dialkyl-phenols with oxygen in the presence ofcatalystcombinations consisting of copper salts and tertiary amines. (See, forexample, West German Offenlegungsschrift (German Published Specification) 2,126,434 and U. S~ Patent 3,306,875).

LeA 16,536 -7-, .. .... . . . . ..... . . . .

Suitable poly-(2,6-dialkyl-1,4-phenylene oxides) are, in particular, poly-[2,6-di(Cl-C~-alky~ ,4-phenylene oxide~, for example, poly-(2,6-dimethyl-1,4-phenylene oxide).

Suitable 2,6-dialkylphenols are, in particular, those with Cl-C4-alkyl substituents, such as, for example, 2,6-dimethylphenol, 2-methyl-6-ethylphenol, 2,6-diethylphenol,
2-ethyl-6-n-propylphenol, 2-methyl-6-isopropylphenol, 2-methyl-6-n-propylphenol, 2-methyl-6-butylphenol and 2,6 di-n-propylphenol. ;

Suitable catalyst combinations are, in particular, copper-I chloride and triethylamine, copper-I sulphate and tributylamine, copper-I sulphate and tributylamine, copper-I
acetate and N-methylmorpholine and copper-I chloride and pyridine.

A suitable process for the preparation of poly-(2,6-dialkyl-1,4-phenylene oxides) is, for example, as follows using copper-I chloride/pyridine as the catalyst combination in accordance with West German Offenlegungsschrift (German Published Specification) 2,126,434:

A 2,6-dialkylphenol is dissolved in a mixture of n-butanol/toluene and condensed by oxidative dehydrogenation inthe presence of the copper-I chloride/pyridine complex with oxygen being supplied. The polyphenylene oxide which has precipitated is then reprecipitated from chloroform/meth~nol.

Polyarylsulphones in the sense of the invention have average weight-average molecular weights Mw (measured by the light scattering method in CHC13) of between about 1,000 and LeA 16,536 , . . .. .. . .

and 200,000, preferably between about 20,000 and 60,000.
Examples of polyarylsulphones are the polyarylsulphones obtainable according to known processes from 4,4'-dichloro-diphenylsulphone and a bisphenol, especially 2,2-bis-(4-hydroxyphenyl)-propane, with average weight-average molecular weights (Mw) of from about 2,000 to 200,000.

Particularly suitable polyarylsulphones in the sense of the invention are branched polyaryl ether-sulphones,which are prepared by reacting together approximately equimolar amounts of at least one aromatic di-alkali metal bis-hydroxy-late and at least one bis-(4-halogenoaryl) compound, the aryl nuclei of which are linked by at least one sulphonyl group, in the presence of about 0.01 mol % to about 2 mol %, pre- -ferably from about 0.05 mol % to about 1.5 mol ~, based on bishydroxylate or on bis-halogenoaryl compound, of at least :
one branching agent, that is to say an alkali metal salt of an aromatic compound which contains three or more than three ~-hydroxyl groups andjor of a halogenoaryl compound with three or more than three aryl-bonded halogen substituents which are replaceable under the reaction conditions for the preparation of the polyaryl ether-sulphone.

If appropriate, for ~xample, a Cl-C4-monoalkyl halide and/or monophenol can also be used, in amounts of from 0.001 to about 5 mol %, based on bishydroxylate or bishalogenoaryl compound, as a chain stopper in the preparation of the branched ~ .
aromatic polyaryl ether-sulphones. The degree of branching of these polyaryl ether-sulphones naturally depends on the amount and the nature of the branching agent employed, that is to say of the aromatic compound containing three or more than three LeA 16,536 -9-~ . .

10~803~

hydroxyl groups and/or of the halogenated aromatic compound containing three or more than three halogen substituents which can be substituted under the conditions for the pre-paration of the polyaryl ether-sulphone. In this way, high-molecular thermoplastics, branched polyaryl ether-sulphones, which are still completely soluble in the customary solvents and which have relative viscosities, measured on solutions of 0.5 g of product in 100 ml of methylene chloride at 25C, of between about 1.15 and about 1.80 and average molecular 1~ weights, measured by means of light scattering, of between about 20,000 and about 120,000, are formed.

Suitable bis-(4-halogenoaryl) compounds for the preparation of branched polyaryl ether-sulphones, the aryl nuclei of which are linked by at least one sulphone group.
are, for example, monosulphones, such as 4,4'-dichlorodi-phenylsulphone or 4,4'-difluorodiphenylsulphone (formula I, n = 0), and dihalogenodiaryldisulphone-aryls of the general formula I

(I) Hal- ~ -SO2 [Arl-SO~ - ~ Hal ~n = 0 or 1) .:~ ;,.:

wherein ;~

n = 1, Hal denotes chlorine or fluorine and Arl denotes a biphenylene or oxybisphenylene radical These compounds are known from the literature.

LeA 16,536 -10-- : , . . : - -.-- - - '- ::

10~8034 Suitable di-alkali metal bishydroxylates (di-alkali metal bisphenolates) for the preparation of the branched polyaryl ether-sulphones are obtained from the diphenols, : such as hydroquinone or resorcinol, but preferably from the compounds of the general formula II

(}I) ~0~ H

wherein R denotes a divalent Cl-C12-alkylene or C2-C12 alkylidene radical, C5-C15 cycloalkylene or CS-C15 cycloalkylidene radical, C7-C12-aralkylene or aralkylidene radical or C8-C12-arylene-bis-alkylidene radical or the grouping -O-, -S-, -SO-, -S02- or -CO- or denotes a single bond.
Examples of diphenols of the formula II which may be mentioned are: bis-(4-hydroxyphenyl)-methane, 1,1-bis-(4-hydroxy-phenyl)-cyclohexane, bis-)4-hydroxyphenyl)-phenylmethane, 4,4'-dihydroxy-diphenyl ether, 4,4'-dihydroxy-diphenyl sulphide, 4,4'-dihydroxy-diphenyl sulphoxide, and 4,4'-dihydroxy-diphenyl benzophenone, but especially 2,2-bis-(4-hydroxyphenyl)-propane, 4,4'-dihydroxydiphenylsulphone t 4,4'-dihydroxydiphenyl and ~,~'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene. Examples which may be mentioned of branching components of the type of an aromatic compound containing three or more than three hydroxyl groups, for the preparation of the branched polyaryl ether-sulphones, are: phloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene-2- (= trimeric isopropenylphenol), 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane (=hydrogenated LeA 16,536 .

~068034 trimeric isopropenyl-phenol), 1,3,5,-tri-(4-hydroxyphenyl)-benzene, l,l,l-tri-(4-hydroxyphenyl)-ethane and l,l,l-tri-(4-hydroxyphenyl)-propane, tetra-(4-hydroxyphenyl)-methane, 1,4-bis-[(4',4"-dihydroxy-triphenyl)-methyl] - benzene (compare West German Offenlegungsschrift (German Published Specification) 2,113,347 (Le A 13,638) and 2,2-bis-/4,4'-bis-(4-hydroxyphenyl)-cyclohexyl/-propane. Halogenaryl compounds having three or more than three aryl-bonded halogen substituents which are re-placeable under the reaction conditions for the preparation of the polyaryl ether-sulphone, which are suitable as branching components for the preparation of the branched polyaryl ether-sulphones, are those in which the halogen substituents are activated by electron-attracting groups; examples which may be mentioned are 1,3,5-tri-(4-chlorophenylsulphonyl)-benzene, 2,4,4'-trichlorodiphenylsulphone and 1-chloro-2,6-bis-(4-chlorophenyl-sulphonyl) - benzene. Activation of the halogen substituent can also be effected, apart from by the sulphonyl group, bit other electron-attracting groups, that is to say those with a positive sigma value. (Company Chem. Rev. 49 ~;~
(1951) page 273 et seq. and Quart. Rev. 12 (1958) 1 et seq.);
substituents having sigma values greater than +l are preferred.

Examples which may be mentioned of alkali metal hydro-xylates derived from aromatic compounds containing two, three or more than three hydroxyl groups are the corresponding sodium hydroxylates or potassium hydroxylates. Examples which may be mentioned of suitable polar organic solvents for the pre-paration of the branched polyaryl ether-sulphones are Le A 16,536 -12-. - . - . -; .
, .

diethylsulphoxide, dimethylsulphone, diethylsulphone, diisopropylsulphone and tetramethylenesulphone, but preferably dimethylsulphoxide. They are used in amounts of from about 1 liter to 5 liters, based on 1 mol of di-alkali metal bis-
3, 5 hydroxylates employed.

: The preparation of the branched polyaryl ether-sulphones is described in detail in West German Offenlegungsschrift ; (German Published Specification) 2,305,413 (Le A 14 799).

The branched aromatic polyaryl ether-sulphones which are suitable according to the invention thus have divalent structural e lements of the formula IV

(IV) ~-Z-O- ~ -52- Arl-5O2 ]~

wherein Arl has the above mentioned meaning, .
` 15 n is 0 or L and z corresponds to a p-phenylene radical, a m-phenylene radical or a divalent radical of the following formula (v) (V) - ~ -R- ~ -in which R has the above mentioned meaning : and wherein X can be an integer between about 1~ and about 1~0.
, Le A 16,536 -13-.. , . . - . ~ . - - .............. , . ~ , ........ .

- -- . : . , , . . . ,: - - . . . .

3 0~8034 The branched aromatic polyaryl ether-sulphones also contain, in amounts of between 0.01 mol % and 2 mol ~, tris-hydroxylate radicals resulting from the incorporation of the branching components or hydroxylate radicals with more than three hydroxylate groups and/or aryl branch radicals which are trivalent or of higher valency and which result from the halogenoaryl compounds which posses three or more than three aryl-bonded halogen substituents which are replaceable under the reaction conditions for the preparation of the polyaryl ether-sulphone.

Polyalkylene glycol terephthalates in the sense of the present invention are, for example, those based on ethylene glycol, propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol and 1,4-bis-hydroxymethylcyclohexane. The molecular weights (Mw) of these polyalkylene glycol terephthalates are : essentially between about 10,000 and 80,000. The polyalkylene glycol terephthalates can be obtained according to known processes,for example, from a terephthalic acid dialkyl ester and the corresponding diol by trans-esterification (See, for example, U. S. Patents 2,647,885, 2,643,989, 2,534,028, 2,578,660, 2,742,494 and 2,901,466).

For example, a lower alkyl ester of terephthalic acid, preferably the dimethyl ester, is used as the starting :
material and this is trans-esterified with an excess of diol in the presence of suitable catalyst to give the bis-hydroxyalkyl ester of terephthalic acid. In this reaction, the temperature, which is initially 140C, is raised to 210-220C. The alcohol which is liberated is distilled off. The LeA 16,536 -14- :~

further condensation is then carried out at temperatures of 210-280C and the pressure is reduced stepwise down to less than 1 mm Hg~ the excess diol being distilled off.

Suitable polystyrenes according to the present invention are homopolymers of styrene or copolymers of styrene with, preferahly, acrylonitrile and/or butadiene, and/or maleic acid esters, which are obtained, for example, from the monomers or, respectively, the mixture of monomers by ~spension poly-merisation in the presence of catalysts, and have essentially an MW of about 10,000 - 600,000. (Mw is measured in DMF at c = 5 g/l and 20C~.

(For literature in this connection see: Beilsteins Handbuch der Organischen Chemi (Beilsteins Handbook of Organic Chemistry), fourth edition, third supplement, Volume 5, pages 1163-1169, Springer Verlag 1964 and H. Ohlinger, Polystyrol :- ;
(Polystyrene) Part 1, Herstellungsverfahren and Eigenschaften der Produkte (Methods of Preparation and Properties of the :
Products), Springer Verlag 1955).

Polyamides which are suitable according to the present invention are, for example, nylon-6,6, which has been pre-pared by condensation of hexamethylenediamine with adipic acid;
nylon-6,10, prepared from hexamethylenediamine and sebacic :
acid; polymers of ~-aminocaproic acid or of ~-caprolactam, so-called nylon-6; polyamide 11, the self-condensation product of ll-aminoundecanoic acid; copolymers of hexamethylenediamine, ~-caprolactam, adipic acid and sebacic acid; copolymers of hexamethylenediamine and adipic acid, modified with formaldehyde and methanol; polyamides, which have been prepared by reacting Le A 16,536 -15-a linear diamine with dimeric acids, which ha~e been obtained from isobutylene dimers, and polyamides, which have been prepared from polymeric unsaturated fatty acids and various polyamines.

All the polyamides which are suitable according to - the invention should contain the -C-NH- grouping as a bridge "
member in the main chain and have average molecular weights (Mw, which is determined gel chromatographically in m-cresol) of between about 1,000 and 100,000. (For literature see, for example, U. S. Patent 3,431,224, column 3, lines 58 - 73).

! The starting materials for the plastic sheets to be used according to the invention are the corresponding glass fiber-filled plastics. These are known or can be obtained according to known processes. (See, for example, DT-AS
¦ 15 (German Published Specification) 1,454,802, U. S. Patent Specification 2,877,501, U. S. Patent Specification 3,453,356 i and DT-AS (German Published Specification) 1,454,789).

The glass fiber content in the thermoplastics which are suitable according to the invention and in the sheets, obtainable therefrom, which are suitable according to the invention, which is between about 5% by weight and 50% by weight, preferably between about 20% by weight and 30% by weight, based on the total weight in each case, can be adjusted by known methods specific points which have to be taken into account being the thickness of the sheets to be produced and the desired diffusing effect.

The production of sheets from the suitable glass fiber-filled thermoplastics, that is to say the glass fiber-filled Le~ 16,536 -16- s ~0~:i8034 polyolefines, cellulose esters, polycarbonates, polyaryl-sulphones, polystyrenes, polyamides, polyphenylene oxides and polyalkylene terephthalates, can be affected according to the customary techniques, for example by extrusion in a commercial available extruder, which preferably has a degassing zone, which is connected to a sheet die via an adapter. After the sheet, which is still plastic has issued from the die, it is allowed to run onto a cooling grid, a chill-roll unit or a three-roll stack, the temperature being lowered to below the softening point of the particular polymer. The sheets solidify and can be rolled up. (See, for example, West German Offen-legungsschrift (German Published Specification) 2,437,508).

The sheets which are suitable according to the invention of the glass fiber-filled thermoplastics can be employed direct as diffusing discs, for example in single and multi-function monitoring instruments or in multi-purpose instruments in motor-driven vehicles. The sheets according to the in~ention can be printed with suitable signal colours or provided with symbols (for example signs or letters) by imprinting.

When coloured or pigmented thermoplastics are used, the sheets which are suitable according to the invention can be obtained as correspondingly colored or pigmented sheets.
Customary dyestuffs and customary pigments are suitable in the customary amounts.

The sheets which are suitable according to the in-vention can be shaped by the thermo-forming process without losing their diffusion effect; this is not possible when delustered sheets are used since the delustering of the sheets is destroyed by the melting required for this purpose.
Le A 16,536 -17-~068034 The diffusing effect of the sheets, which are suit-able according to the invention, of glass fiber-filled thermoplastics can be varied over a wide range, for example, by changing the thickness of the sheets and/or by changing the glass fiber content of the sheets; the diffusion effect is measured for example, using a spectrophotometer which is fitted with an Ulbrichtsphere attachment.

The proportion of the transmitted light (transmission) which is deflected from the direction of incidence is measured in the range of visible light, The diffusing effect of the sheets which are suitable according to the invention is adequate when it is no longer possible, using the above mentioned measuring device, to record the proportion of the light which passes direct through the sample.

The tests showed that the diffusing effect was ~`
adequate when there was a linear increase in the transmission of the deflected portion between 350 nm and 700 nm. Thus, for example, the transmission of the portion deflected light obtained at 350 nm is 15% and at 700 nm is 30% for suitable sheets.

Another very simple means of assessing the diffusing effect is visually, by setting up the diffusing disc 4 cm in front of an incandescent light with a bulb diameter of 20mm and a power of 30 watts.

When the diffusing effect is adequate, an observer can no longer discern the filament of the lighted incandescent LeA 16,536 -18-... . . , ......... . . : -:: ~ - . . . .:: . . . -.: : . - . - ~ -~,. , .,, .... . - : . .

:L068034 lamp behind the disc when he is at a distance of >25 cm from the sheet.

Preparation of the starting materials:
A. Instructions for the prep-a--r-atlon of a polycarbonate About 454 parts of 4,4'-dihydroxydiphenyl-2,2-propane and 0.5 parts of p-tert.-butylphenol are suspended in 1.5 1 of water. In a 3 necked flask, fitted with a stirrer and a gas inlet tube, the oxygen is removed from the reaction mixture by passing nitrogen through the reaction mixture for 15 minutes, while stirring. 355 parts of 45% strength sodium hydroxide solution and 1,000 parts of methylene chloride are then added. The mixture is cooled to 25C. While maintaining this temperature by cooling, 237 parts of phosgene are added over a period of 120 minutes. An additional amount of 75 parts of a 45% strength sodium hydroxide solution is added after 15 - 30 minutes or after the absorption of phosgene has started. 1.6 parts of tri-ethylamine are added to the resulting solution and the mixture is stirred for a further 15 minutes.
A highly viscous solution is obtained, the viscosity of which is regulated by adding methylene chloride. The aqueous phase is separated off. The organic phase is washed with water until free from salt and alkali. The polycarbonate is isolated from the washed solution and dried. The polycarbonate has a relative viscosity of 1.29 - 1.30, measured in a 0.5~ strength solution in methylene chloride at 20C. This corresponds approximately to a molecular weight Mw of 32,000. The polycarbonate thus obtained is extruded and granulated. (In these instructions parts are parts by weight and strength is w/w).

LeA 16,536 -19-., : : . . - .::
:- : :,, -. : . .

B. Instructions for the ~reparation of a polysulphone (with the addition of 1 mol % of trisphenol) 57.075 g (0.25 mol) of 2,2-bis-(4-hydroxyphenyl)-propane and 0.871 g (0.0025 mol) of 2,6-bis-(2'-hydroxy-5'-s methylbenzyl)-4-methyl-phenol are weighed into a metal vessel and dissolved in 500 ml of dimethylsulphoxide. The vessel is provided with a gas inlet tube, a stirrer, a thermometer, a reflux condenser and a water collecting device filled with toluene. A slow stream of nitrogen is then passed through the apparatus in order to produce an inert gas atmosphere.
20.03 g (0.5 + 0.0075 mol) of sodium hydroxide are added in the solid form or as a concentrated aqueous solution and, after the sodium hydroxide was dissolved, 150 mol of toluene are added dropwise. The reaction mixture thus obtained is heated to a temperature of 140 to 150C for 6 hours, the water contained in the reaction mixture and the water formed ~-during ~he formation of the phenolate being distilled, with the toluene as an azeotrope, continuously into the water l ;
collecting device, where it settles out, while the toluene runs back again into the reaction mixture. When all the water has been removed from the reaction system, the water collecting vessel is emptied, the toluene is distilled off and a solution of 72.882 g (0.25 + 0.00375 mol) of 4,4'-dichlorodiphenylsulphone in 100 ml of anhydrous dimethyl-sulphoxide is added at a temperature of 120 - 140C. The mixture is then heated gradually, while stirring, to a reaction temperature of 150C. The reaction mixture is left at this temperature for 6 hours, the sodium chloride formed during the condensation settling out rapidly. When the reaction is complete, the cooled polymer solution is introduced into rapidly stirred LeA 16,536 -20-:, ~ . . . . . :, . -.. -.: , . . .: :.-. . . ................. . :
..... .: ''.. : ' ~ :,: . ,.... ,,, ~ , water, the resulting polyaryl ether-sulphone settling out in a solid form. It is filtered off, washed carefully and dried in ; vacuo. For purification, the polysulphone obtained is dissolved in methylene chloride the solution is filtered and the filtrate is poured into an excess of rapidly stirred methanol. The ; polysulphone separates out as white flakes. It is filtered off and dried.

C. Instructions for the preparation of a cellulose ester 500 g of cellulose are introduced into a mixture of 1.8 kg of acetic anhydride, 2 kg of glacial acetic acid and 17 g of concentrated sulphuric acid and the mixture is left to stand for 24 hours a clear viscous solution being formed, from which the chloroform-soluble primary acetate can be precipitated by adding water, after dilution wi~h a little glacial acetic acid. In order to obtain the acetone-soluble secondary acetate, 350 g of water and 350 g of glacial acetic acid and an amount of Na acetate sufficient to convert the sulphuric acid into the bisulphate are added to the acetylation mixture and the mixture is left to stand at 65 - 70C for 3 to 5 days until a sample precipitated with water proves to be soluble in acetone. ~Ost, Zeit~chr. Agnew. Chem. 32,69 (1919).
D. Instructions for the pre~aration_of a po ~-(2,6-dialk~l-1,4-phenylene oxide) Poly-(2,6-dimethyl-1,4-pehnylene oxide) prepared in accordance with West German Offenlegungsschrift (German Published Specification) 2,126,434:
8 kg of 2,6-dimethylphenol were dissolved in a solution of 3C 1 of n-butanol, 10 1 of toluene, 4 kg of pyridine and 100 g of copper-I chloride. ~y supplying 50 1 of oxygen/minute LeA 16,536 ~ -21-1068~34 for a period of 6 hours, 2,6-dimethylphenol is condensed by oxidative dehydrogenation to give poly-(2,6-dimethyl-1,4-penylene oxide). The temperature rises sharply when oxygen is first passed in. A rise in temperature of above 55C is avoided by cooling during the first reaction state. The poly-phenylene oxide starts to precipitate out after 2 to 3 hours.
After supplying oxygen for about a further 3 hours, the poly-pheynlene oxide is filtered off, washed pyridine-free with methanol acidified with hydrochloric acid and reprecipitated from chloroform/methanol. A pale yellow-colored powder is obtained. The viscosity nrel is 1-2 (~rel measured at 25C
in methylene chloride at a concentration of 5 g/l) and the - -molecular weight Mw is about 60,000.
E. Instructions for the preparation of a polyolefine According to F. A. Henglein, "Grundlagen der ~ -Verfahrenstechnik" ("Basic Principles of Process Technology"), Verlag Chemie, Weinheim 1963, it is possible to produce, for example, polyethylene from ethylene as follows:
1. By the high pressure process (ICI process).
In this process the ethylene which is compressed to 1,000-2,000 atmospheres gauge is polymerized continuously, for example in a tube system (BASF process) at 180 - 200 using traces of oxygen as the initiator and is discharged as a liquid.
2. By the low pressure process using Ziegler catalyst [literature in this connection: Belgian Patents 533,362 (1955),534,792 (1955) and 540,459 (1955)].
In this process the polymerization is carried out at 10-15 atmospheres gauge and 20 - 80C in paraffin hydro-LeA 16,536 -22-. .
. : .. . : ~

10~i8034 carbons with the addition of aluminum triethyl and titanium tetrachloride as the catalyst. The polyethylene precipitates as white flakes during the polymerization and must be subjected to a separate washing process with the alcoholic hydrochloric acid in order to remove catalyst residues.

A polyethylene obtained according to process E 1 has, -for example, a MW (measured by the light scattering method) of 10,000 - 1,000,000 and a polyethylene obtained according to process E 2 has, for example, a Mw (measured by the light scattering method) of 1,000 to 500,000.
F. Instructions for the preparatlon of a polyalkylene glycol terephthalate, that is to say for_polyethy-ene ~l~col terephthalate:
97 parts of terephthalic acid dimethyl ester, 71 parts of ethylene glycol, 0.15 parts of anhydrous calcium acetate and 0.4 part of antimony trioxide are filled into a round-bottomed flask fitted with a distillation attachment, an air-cooled condenser and a gas inlet capillary. The air is removed from the apparatus by evacuating and filling with nitrogen. The components are melted by heating to 170C.
A slow stream of nitrogen is paSsed through the capillary.
The methanol which is formed during the trans-esterification, which starts immediately, is distilled off. After about 1 hours, the elimination of methanQl subsides and the temperature is raised to 200C for 2 hours, the remaining methanol being removed. Excess ethylene glycol is then distilled off at 220C and the temperature is raised to 280~C. At this temperature the apparatus is gradually evacuated to about 0.3 mm LeA 16,536 -~3_ 1068{~34 Hg. The reaction is complete after a further 3 hours. The polyethylene terephthalate obtained has a relative visc08ity of 2.10, mea~ured at 25C using a 1% strength solution in a solvent mixture consisting of equal parts of phenol and tetrachloroethane. This corresponds approximately to a molecular weight Mw of 28,000. (In these instructions parts ~ -or parts by weight and strength is w/w). I
G. Instructions for the pre~aration of a suitable copolymer ~- -,j . ~ .
of styrene and acrylonitrile: -The preparation i~ carried out by emulsion poly- !
merization of the following batch consisting of 2,000 kg of deionized water, 815 kg of styrene, 19.5 kg of sodium oleate, ! :;
350 kg of acrylonitrile, 5.7 kg of a 50% strength by weight aqueous solution of sodium hydroxide, 1.2 kg of potassium j 15 persulphate and 1.3 kg of sodium pyrophosphate and 22.3 kg of tert.-dodecylmercaptan.

This mixture, the pH of which is adjusted to 9 with sodium hydroxide solution, is heated to 60C in a pressure kettle, while stirring. The polymerization starts at an internal temperature of about 70C. During the course of the polymeriz-ation care is taken, by means o~ appropriate cooling, that the temperature does not exceed 70 - 72C. About 2-1/2 hours after the start of polymerization the mixture is heated up to 95 - 100C and the residual monomers are then evaporated in the course of half an hour. The resulting polymer has a MW ~measured in DMF; c - 5 ~ pecific of 150,000. (In these instructions strength is w~w).

(For literature in this connection see the book "Polystrol" (Polystyrenen) by H. Ohlinger, which has already LeA 16,536 _~4_ ~,.. , - , . , - . . ., , , . . -10t;8034 been mentioned).
H. Instruction for the preparation of a polyamide from ~-caprolactam 190 g of ~-caprolactam and 10 g of ~-aminocaproic acid are weighed into a 500 ml flask and the flask is heated in a metal bath of 270~C. After 4 - 5 hours the condensation has proceeded to such an extend that a viscosity of ~rel =
2.6,2.7 (nrel is measured on a solution of 1 g of extract-free polycaprolactam in 100 ml of cresol) is obtained. The resulting molecular weight ~w is about 16,000. The melt is discharged from the flask, granulated and extracted with methanol. (For literature in this connection see: Houben-Weyl, Methoden der Organischen Chemie (Methods of Organic Chemistry), Volume 14/2, Makromolekulare Stoffe (Macromolecular Substances), Georg Thieme Verlag, 1~63, pages 119 et seq.).

The corresponding glass fiber-filled plastics can be obtained from the thermoplastics obtained according to instructions A to H by incorporating the glass fibers, which are suitable according to the invention, in the desired amounts in accordance with the processes of West German Auslegeschrift (German Published Specification) 1,454,802, or of U. S. Patent Specification 2,877,501 or of U. S. Patent Specification 3,435,356.

Preparation of the sheets according to the invention:
Example 1 Polycarbonate based on bisphenol A and having a relative viscosity ~rel = 1.32 (Measured in CH2C12 at 25C

using 0.5 g in 100 ml), which has a glass fiber content of 20% of short glass fibers with water size (compare West German LeA 16,536 -25-Auslegeschrift (German Published Specification) 1,201,991) is melted in dn extruder with a three zon~ ~crc~which has a compression ration of 1 : 3. The cylinderitemperature is set at 260~C in the feed zone and at 280DC in the compression and 5 metering zones. The temperature of the sheet die used is set --at 280C over the entire die width. When the scre~ rotates at 60 rpm, the take-off speed of the three-roll stack is so adjusted that a 0.4 mm thick sheet is obtained. This sheet has a smooth surface on both sides. For visual assessment of the diffusing effect of the sheet produced in this way, the sheet is placed 4 cm in front of an incandescent lamp with a bulb diameter of 20 mm and a power of 30 watts. From a distance of >25 cm from the sheet, an observer can no longer discern the filament of the lighted incandescent lamp behind the sheet. When the light transmission of the sheet is measured it is found that there is uniform diffusion over the entire wavelength range. The transmission is 10%
at 350 nm and 22% at 700 nm.

Example 2 _ Analogously to Example 1, a polycarbonate based on bisphenol A and having a viscosity of nrel = 1-28 (measured in CH2C12 at 25C using 0.5 g per 100 ml) and a glass fiber content of 10% by weight of short glass fibers with water size is employed as the polymer. On visual assessment, the 0.~ mm thick sheet obtained shows the same diffusing effect as in Example l; measurement of the transmitted light ~transmission) gives a value of 15% at 350 nm and a value of 30% at 700 nm.

Example 3 Analogously to Example 1, a cellulose propionate LeA 16,536 -26-i - - - . . . .
- .- . ~ . . : . ., .- . : . , 10~8034 which has an acetic acid content of 5% by weight, a propionic acid content of 59% by weight, a plasticiser content of 10%
by weight and a glass fiber content of 20~ by weight of short glass fibers is employed as the polymer. In all temperature zones, the processing temperatures are set 50C lower than those used in Exampl~ 1. A 0.1 mm thick sheet is produced from this material. On visual assessment of the diffusing effect, the filament of the incandescent lamp placed behind the sheet can still be discerned very faintly when the test arrangement mentioned in Example 1 is used. The transmitted light (transmission) is 30~ at 350 nm and 56% at 70 nm.

E~ample 4 Analogously to Example 1, a polyarylsulphone prepared from bisphenol A and 4,4-dichlorodiphenylsulphone (Mw 40,000) and having a 20% by weight glass fiber content is employed as the polymer . The processing temperature is set 20C higher than in Example 1. The sheet is taken off yia a chill-roll installation, the roller temperature of the take-off device being raised to 150C. Spherical caps with a diameter of 10 mm and a height of 5 mm are produced by the thermoforming process from the 0.4 mm thick sheet produced in thi~ way.
The filament of a signal lamp which is placed at a distance of 1 cm behind this shaped sheet and which has a power of 12 watts can no longer be discerned. Transmission is 20% at 350 nm and 40% at 700 nm.

Further ~heets can be pxoduced by modifying E~ample 1 -~
so that the other thermoplastics mentioned in the application -are employed in place of polycarbonate and in addition, the ;
glass fiber content is varied within the ran~e according to the inventiOn.
LeA 16,536 -27-Although the invention has been described in detail for the purpose of illustration, it is to be understood that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

.. . .

LeA 16,536 -28-

Claims (9)

The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:
1. A process for the production of diffusing discs comprising forming the discs from about 30 µm to 1,000 µm thick sheets of glass fiber-filled thermoplastics selected from the group consisting of a cellulose ester having a ?w of about 10,000 to 1,000,000, a polycarbonate having a molecular weight (?w) of between about 10,000 and 100,000, a polyaryl-sulphone having a molecular weight (?w) of between about 1,000 and 200,000, a polyphenylene oxide having a molecular weight (?w) of about 2,000 to 100,000, and a polyalkylene terephthalate having a molecular weight (?w) of about 10,000 to 80,000 with between 20% by weight and 30% by weight, based on the total weight of the glass fiber-filled thermoplastic, of glass fiber selected from the group consisting of glass fibers with an average fiber length of between 60 mm and 6 mm and glass fibers with an average fiber length of between 5 mm and 0.5 mm.
2. The process according to Claim 1, wherein the glass fiber is selected from the group consisting of glass fibers with an average fiber length of 6,000 µm, a diameter of 15 µm and a powder content (<50 µm) of about 1% by weight and glass fibers with an average length of 230 µm, a diameter of 13 µm and a powder content (<50 µm) of 5%
by weight.
3. The process according to Claim 1, wherein the thermoplastics contain a dyestuff or pigment.
4. The process of Claim 1, wherein the glass fibers are short and the resin is selected from the group consisting of aromatic polycarbonate, cellulose propionate and polyaryl-sulphone.
5. The process of Claim 1, wherein the poly-phenylene oxide is a poly-(2,6-dialkyl-1,4-phenylene oxide).
6. A diffusing disc in which the proportion of light incident on the disc which passes directly through the thickness of the disc is not measurable with a spectro-photometer produced by incorporating about 20 to 30 weight %, based on the total weight of filled thermoplastic, of glass fibers selected from the group consisting of glass fibers with an average fiber length of between 60 mm and 6 mm and glass fibers with an average fiber length of be-tween 5 mm and 0.5 mm into a thermoplastic resin selected from the group consisting of a cellulose ester having a molecular weight (?w) of about 10,000 to 1,000,000, a polycarbonate having a molecular weight (?w) of between about 10,000 and 100,000, a polyaryl-sulphone having a molecular weight (?w) of between about 1,000 and 200,000, a poly-phenylene oxide having a molecular weight (?w) of about 2,000 to 100,000 and a polyalkylene terephthalate having a molecular weight (?w) of about 10,000 to 80,000, forming the resin into a sheet with a thickness of between about 30 and 1,000 µm and forming said disc from the sheet.
7. The diffusing disc of Claim 6, wherein there is a linear increase in the transmission of the deflected portion of light incident on the disc between 350 nm and 700 nm.
8. In an apparatus for diffusing light via a diffusing element, the improvement wherein said diffusing element is a diffusing disc in which the proportion of light incident on the disc which passes directly through the thickness of the disc is not measurable with a spectro-photometer and said disc is produced by incorporating about 20 to 30 weight %, based on the total weight of filled thermoplastic, of glass fibers selected from the group consisting of glass fibers with an average fiber length of between 60 mm and 6 mm and glass fibers with an average fiber length of between 5 mm and 0.5 mm into a thermoplastic resin selected from the group consisting of a cellulose ester having a molecular weight (?w) of about 10,000 to 1,000,000, a polycarbonate having a molecular weight (?w) of between about 10,000 and 100,000, a polyaryl-sulphone having a molecular weight (?w) of between about 1,000 and 200,000, a polyphenylene oxide having a molecular weight (?w) of about 2,000 to 100,000 and a polyalkylene tere-phthalate having a molecular weight (?w) of about 10,000 to 80,000, forming the resin into a sheet with a thickness of between about 30 µm and 1,000 µm and forming said disc from the sheet.
9. The light diffusing apparatus of Claim 8, wherein the apparatus is selected from the group consisting of single- and multi-function monitoring instruments and flow sheet panels.
CA255,344A 1975-07-12 1976-06-21 Production of diffusing discs using sheets of glass fiber-filled thermoplastics Expired CA1068034A (en)

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DE2721885C3 (en) * 1977-05-14 1981-12-24 Bayer Ag, 5090 Leverkusen Manufacture of lens diffusers
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JPS57133149A (en) * 1981-02-12 1982-08-17 Idemitsu Kosan Co Ltd Polycarbonate resin composition
NL8300817A (en) * 1983-03-07 1984-10-01 Philips Nv PROJECTION SCREEN.
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US6550938B2 (en) * 2000-02-09 2003-04-22 Lexalite International Corporation Lighting fixture employing a partially reflective partially transmittive polymeric reflector
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