Method of making photochromic thermoplastics
First Claim
1. A method of making a photochromic thermoplastic material comprising the steps of:
- extruding a length of thermoplastic material comprising a first part, a second part and two cross-sectional dimensions, at least one of which is small in relation to the length;
treating the first part of said length with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material;
during said treating step, drying the second part of said treated length to evaporate the solvent; and
cutting the dried length into smaller pieces having photochromic properties.
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Abstract
A method of making photochromic thermoplastic wherein the material is extruded into a length or lengths having at least one relatively small cross-sectional dimension. The length or lengths are treated with a solution of photochromic dye dissolved in a solvent, for example, cyclohexanone, which attacks the material. The length or lengths have a surface area-to-volume ratio sufficiently large to absorb an effective amount of the dye at their surface or surfaces. The length or lengths are dried to evaporate the solvent. The length or lengths are heated during the treating and drying steps. The dried length or lengths are cut into smaller pieces which may be introduced directly into a molding machine to form photochromic articles. Where a plurality of lengths are provided, the surfaces thereof are maintained separated from one another during the treating and drying steps.
27 Citations
32 Claims
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1. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding a length of thermoplastic material comprising a first part, a second part and two cross-sectional dimensions, at least one of which is small in relation to the length;
treating the first part of said length with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material;
during said treating step, drying the second part of said treated length to evaporate the solvent; and
cutting the dried length into smaller pieces having photochromic properties. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
providing pellets of the thermoplastic material; and
extruding said pellets into said length.
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12. A method as in claim 11, wherein the thermoplastic material has a melting temperature and wherein the method further includes the step of heating the pellets to the melting temperature during the extruding step.
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13. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding a plurality of lengths of thermoplastic material comprising a surface and two cross-sectional dimensions, at least one of which is small in relation to each of the lengths;
treating said lengths with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material; and
drying the solvent off of said lengths, wherein the surfaces of said lengths are maintained separated during the drying step. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
providing pellets of the material; and
extruding said pellets into said lengths.
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26. A method as in claim 25, wherein the thermoplastic material has a melting temperature and wherein the method further comprises the step of heating the pellets to the melting temperature during the extruding step.
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27. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding a length of thermoplastic material comprising two cross-sectional dimensions, at least one of which is small in relation to the length;
treating said length with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material, wherein the solvent has a boiling temperature and the length is heated to a temperature less than the boiling temperature during said treating step;
drying said treated length to evaporate the solvent; and
cutting the dried treated length into smaller pieces having photochromic properties.
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28. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding a length of thermoplastic material comprising two cross-sectional dimensions, at least one of which is small in relation to the length;
treating said length with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material, drying said treated length to evaporate the solvent, wherein the solvent has a boiling temperature and the thermoplastic has a melting temperature and wherein the length is heated during the drying step to a temperature greater than said boiling temperature but less than said melting temperature to increase the rate of evaporation of solvent from a surface of the length during said drying step; and
cutting the dried treated length into smaller pieces having photochromic properties.
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29. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding a plurality of lengths of thermoplastic material comprising a surface and two cross-sectional dimensions, at least one of which is small in relation to the lengths;
treating said lengths with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material; and
drying the solvent off of said lengths, wherein the surfaces of said lengths are maintained separated during the treating and drying steps.
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30. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding a plurality of lengths of thermoplastic material comprising a surface and two cross-sectional dimensions, at least one of which is small in relation to the lengths;
treating said lengths with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material, wherein the surfaces of said lengths are maintained separated during the treating step, wherein the solvent has a boiling temperature and each length is heated to a temperature less than the boiling temperature during the treating step; and
drying the solvent off of said lengths.
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31. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding a plurality of lengths of thermoplastic material having two cross-sectional dimensions, at least one of which is small in relation to the lengths, each length having a surface;
treating said lengths with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material, wherein the surfaces of said lengths are maintained separated during the treating step; and
drying the solvent off of said lengths, wherein the solvent has a boiling temperature and the thermoplastic has a melting temperature and wherein each length is heated during the drying step to a temperature greater than said boiling temperature but less than said melting temperature.
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32. A method of making a photochromic thermoplastic material comprising the steps of:
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extruding one or more lengths of thermoplastic material, each length comprising a surface and two cross-sectional dimensions, at least one of which is small in relation to the one or more lengths;
treating said one length with a solution comprising a photochromic dye dissolved in a solvent which affects said thermoplastic material; and
drying the solvent off of said one length while maintaining the surface of said one length separated from any other lengths.
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Specification