Method for producing article and semi-finished product made of cellulose acetate

Abstract

To provide a method for producing an article and a semi-finished product made of cellulose acetate, capable of recycling a waste material or a processing by-product derived from processing of the semi-finished product made of cellulose acetate.SOLUTION: A method for producing an article and a semi-finished product made of cellulose acetate includes the steps of: recovering a waste material consisting of cellulose acetate derived from previously made cellulose acetate articles and / or semi-finished products; distributing or arranging a mixture of at least one polymeric material inside a mold; and heating and pressing the mixture inside the mold in order to form the article or the semi-finished product. The mixture is formed at least partially by the waste material consisting of cellulose acetate, and the article and / or the semi-finished product may be subjected to a cooling and pressing step. The mixture is formed at least partially by fragments of cellulose acetate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing articles and semi-finished products made from cellulose acetate using exclusively or at least in part waste or processing by-products derived from previously manufactured articles and / or semi-finished products.

[0002] Preferably, the waste used in the present invention originates from the processing of semi-finished products made from cellulose acetate for the manufacture of eyeglass frames. [Background technology]

[0003] In the field of eyeglass manufacturing, it has been known for some time to use cellulose acetate as a material for manufacturing the end tips, side arms and front pieces of eyeglass frames.

[0004] Cellulose acetate is an acetate ester of cellulose that is initially obtained by reacting cellulose with acetic acid and acetic anhydride in the presence of sulfuric acid.

[0005] At least two methods are provided for the manufacture of end tips, side arms, and front pieces of eyeglass frames made from cellulose acetate. Both manufacturing methods involve the use of virgin cellulose acetate, i.e., cellulose acetate that has not previously been used in other manufacturing processes.

[0006] The first method, which is also the preferred method, involves cutting a semi-finished product of cellulose acetate, i.e., a sheet or board, using a pantograph having a profile corresponding to the shape of the resulting end tips, side arms and front pieces.

[0007] A pantograph is a numerically controlled machine tool that can be programmed to perform different cuts in the sheet depending on the frame model being created.

[0008] The end tips, side arms and front pieces thus obtained may be subjected to further successive machining steps depending on the aesthetic appearance of the resulting frame.

[0009] The cellulose acetate semi-finished products, i.e., sheets, have a predetermined size and thickness and are obtained by one or more processes for rolling a mixture of cellulose acetate.

[0010] If frames of various colors are required, a mixture of cellulose acetates of different colors can be mixed together and the mixed mixture can be rolled to obtain the starting sheet.

[0011] One drawback of this solution lies in the fact that mixtures of cellulose acetate of different colors are complicated to prepare and therefore particularly costly.

[0012] Another drawback of this manufacturing method lies in the fact that a large amount of waste is formed during the cutting of the cellulose acetate sheets and subsequent processing steps.

[0013] This waste is not reused and forms waste that must be disposed of through routine procedures, which increase costs and overall processing time.

[0014] A further drawback lies in the fact that sheets or mixtures not used in the manufacturing process remain in storage before being disposed of as waste, which represents a significant expenditure of economic resources for the company.

[0015] The second method involves injecting a liquid or fluid polymer material, such as cellulose acetate, into a mold whose shape corresponds to the shape of the frame to be produced. This method is particularly used for frame models that need to be produced in large quantities.

[0016] The first drawback of this further manufacturing method lies in the fact that it is not particularly suitable for use in the manufacture of frames with various colors, and therefore this manufacturing method is limited to the manufacture of frames with a single color in particular.

[0017] If desired, the frames obtained by this second method may subsequently be varnished, although cellulose acetate is not particularly suitable for undergoing successive varnishing steps, which may result in a less than satisfactory final aesthetic result.

[0018] A further drawback lies in the fact that different frame models necessarily have to be produced using different moulds.

[0019] This drawback makes this second manufacturing method significantly unproductive, especially when a small number of frames must be manufactured.

[0020] Another drawback resides in the fact that the operator cannot define a predetermined program for the dispensing of the polymer material inside the mold before injecting the material. Summary of the Invention [Problem to be solved by the invention]

[0021] SUMMARY OF THE INVENTION It is an object of the present invention to substantially solve the problems of the prior art and overcome known drawbacks by providing a method for producing articles or semi-finished products made from cellulose acetate.

[0022] A particular object of the present invention is to provide a method for producing articles and semi-finished products made from cellulose acetate that allows for the recovery of cellulose acetate from previously produced articles and / or semi-finished products.

[0023] A further object of the present invention is to provide a method for producing articles and semi-finished products made from cellulose acetate that allows for recycling of waste or processing by-products resulting from the processing of semi-finished products made from cellulose acetate.

[0024] A further object of the present invention is to provide a method for producing articles and semi-finished products made from cellulose acetate which is less costly than known methods of the prior art.

[0025] A further object of the present invention is to provide a method for producing articles and semi-finished products made from cellulose acetate which makes it possible to reduce warehouse stock of materials and semi-finished products used in the manufacturing process.

[0026] Another object of the present invention is to provide a method of the above kind that can be used to manufacture various types of eyeglass frames, which may include different colors or groups of colors.

[0027] A further object of the present invention is to provide a method of the above kind which makes it possible to produce articles having structural properties similar to those of articles obtained using virgin cellulose acetate.

[0028] Another object of the present invention is to provide a method of the above kind which makes it possible to produce cellulose acetate articles or semi-finished products using machinery and equipment commonly used in the field.

[0029] A further object of the present invention is to provide a method for the production of articles and semi-finished products made from cellulose acetate, which allows the definition of a predetermined program for the dispensing of material. [Means for solving the problem]

[0030] The above-mentioned objects and objectives are achieved by a method for producing articles and semi-finished products made from cellulose acetate according to claim 1.

[0031] The present invention relates to a method for producing articles and semi-finished products made from cellulose acetate. DETAILED DESCRIPTION OF THE INVENTION

[0032] In particular, the articles obtainable by the manufacturing method are preferably end tips, side arms and front pieces for eyeglass frames, or the articles may be commonly used objects such as combs, clips, fasteners and beauty accessories, or wearable objects such as necklaces, bracelets, earrings and rings.

[0033] The semi-finished products obtainable using the manufacturing method according to the invention preferably comprise sheets suitable for cutting and processing to produce end tips, side arms and front pieces of eyeglass frames.

[0034] However, the method according to the invention can also be used to produce articles and semi-finished products other than those shown above without departing from the scope of the invention.

[0035] The method first involves recovering waste or materials resulting from previously manufactured cellulose acetate articles and / or semi-finished products. This material may also consist of processing by-products.

[0036] The waste may include shavings, shavings and / or cuttings resulting from the processing of semi-finished products for the production of end tips, side arms and front pieces of eyeglass frames, or end tips, side arms and / or front pieces of old eyeglasses that must be discarded.

[0037] Alternatively, the waste may comprise semi-finished products in the form of sheets and / or sheet pieces intended for the manufacture of eyeglass frames.

[0038] However, the waste may also be formed by heterogeneous combinations of the waste materials previously mentioned, i.e., shavings, shavings, cuttings, and / or sheets or sheet pieces, and / or end tips, side arms and front pieces of old frames.

[0039] The method also includes: dispensing or placing a mixture of at least one polymeric material into a mold, the mixture being at least partially formed from cellulose acetate waste material; heating the mixture in the mold; pressing the mixture in a mold to form a workpiece or article; cooling or pressurizing the article or semi-finished product; Includes.

[0040] According to the invention, the mixture is at least partly formed by waste fractions consisting of cellulose acetate.

[0041] In the present invention, the term "mixture" is understood to mean a collection of intermixed solid components in which each component maintains its essential chemical properties.

[0042] Upstream of the dispensing step, the method may also include a step of grinding and / or crushing the waste or processing by-products to obtain fragments of cellulose acetate, so that the mixture dispensed or placed into the mold is in solid form and is at least partially formed by fragments of the recovered cellulose acetate fragments.

[0043] In particular, when the waste material is formed by sheets, sheet pieces, or side arms, end tips and front pieces of frames, it is preferable to carry out a crushing step.

[0044] The grinding and / or crushing steps can be carried out using equipment known in the art and will not be described in detail herein.

[0045] Preferably, the particle size of the waste fragments obtained after the crushing and / or shredding process may be between 1 mm and 50 mm.

[0046] The pieces originating from the waste and included in the mixture may also have different dimensions and / or particle sizes, as well as different colours.

[0047] This particular feature results from the fact that the pieces can come from different waste materials, as mentioned above, making it possible to obtain articles or semi-finished products with a variety of colors and patterns.

[0048] In this regard, the method may include an additional step of screening and separating the waste fragments upstream of the step of dispensing the mixture into the interior of the mold so as to use only fragments having the desired size and / or color.

[0049] For example, sorting of fragments based on fragment size can be done manually or using known optical devices or sieves, and in a similar manner, sorting of fragments based on color can be done manually or using known optical devices.

[0050] The mixture may be at least partially formed by fragments of cellulose acetate derived from waste materials, mixed with polymeric material in the form of granules and / or chips.

[0051] The polymeric material may consist of virgin cellulose acetate in the form of granules and / or pieces, and thus in this embodiment the articles and semi-finished products are made entirely from cellulose acetate.

[0052] The cellulose acetate granules can be of the same type as those used in the manufacture of cellulose acetate articles and semi-finished products known in the art.

[0053] However, in the present mixture, the waste or processing by-product fragments constitute a predominant amount compared to the virgin cellulose acetate granules, and preferably the mixture comprises waste fragments by weight in the range of 50% to 95% by weight, even more preferably 70% to 95% by weight of the total weight of the mixture.

[0054] In some applications, the weight of waste fractions contained in the mixture may also be greater than 95% of the total weight of the mixture.

[0055] Virgin cellulose acetate granules that may be included in the mixture act as a binder within the mixture, allowing the waste pieces to be combined during the heating and pressure steps.

[0056] The polymeric material mixed with the waste fragments may also be different from virgin cellulose acetate without departing from the scope of the present invention.

[0057] Alternatively, the mixture may be formed solely by cellulose acetate fragments derived from waste materials, so that the weight of the fragments in this embodiment is approximately equal to 100%, even taking into account the presence of impurities.

[0058] During the dispensing step, the mixture containing the waste fragments is dispensed into a receiving cavity having a predetermined shape corresponding to the shape of the article or semi-finished product to be obtained, this dispensing step being carried out with this mixture at room temperature.

[0059] Preferably, the size / particle size of the crushed pieces may also be selected upstream depending on the size and configuration of the receiving cavity.

[0060] In a manner known per se, the mould comprises, in addition to the receiving cavity formed or produced in a first part, another part having a punch designed to press the mixture inside the cavity.

[0061] Advantageously, the receiving cavity may be formed in a tray, which may be removably placed inside the mould or which may be arranged to form part of the mould.

[0062] In particular, the tray is intended to be removably placed in the first part of the mold, or the tray may form the first part of the mold and is intended to be directly joined to the part of the mold that comprises the punch.

[0063] Preferably, the dispensing or placing step is carried out at room temperature by dispensing the mixture containing the waste fragments in a tray.

[0064] Thus, the dispensing or placement process of the present invention is performed while the mold is open or not yet assembled, unlike what occurs in injection molding, and in this regard, an operator can manually dispense and place the waste pieces in the tray.

[0065] Advantageously, the dispensing or placing step can also be carried out by placing a template with a predetermined profile in the receiving cavity of the tray before the heating and pressure steps.

[0066] In this way, pieces and / or granules of polymeric material having a predetermined color and size can be placed in a predetermined arrangement in the tray so as to subsequently obtain a predetermined pattern on the article or semi-finished product.

[0067] Preferably, the heating and pressing steps may be performed simultaneously using a press having a heated surface, in which a first portion of the mold having the receiving cavity may be attached to the bottom heated surface of the press, while the mold portion having the punch may rest on the top heated surface of the press.

[0068] In embodiments in which the first portion of the mold is formed by a tray, the tray may be attached directly to the bottom heated surface of the press by a mold holder on the tray.

[0069] Advantageously, the heating and pressure steps can be carried out at heating temperature values ​​between 120° C. and 170° C. and pressure values ​​between 10 bar and 120 bar, depending on the pressure step.

[0070] Preferably, the temperature value is between 140° C. and 165° C. and the pressure value is between 20 bar and 100 bar depending on the pressure step.

[0071] These operating conditions allow the mixture to be passed from room temperature to a temperature for softening the mixture, i.e., the mixture of waste fragments and, if present, optionally virgin cellulose acetate granules, so that a malleable mass of material is formed.

[0072] This mass of malleable material is simultaneously pressed to form a blank or article.

[0073] Advantageously, the operating conditions used in the heating and pressure steps are such as to maintain the temperature of the cellulose acetate below its melting temperature, i.e. at least 175°C, in order to avoid degradation of the cellulose acetate.

[0074] The cooling and pressing steps are preferably carried out in a further mould containing a respective part with a punch, e.g. by transferring a tray to that further mould, and at the end of the pressing and heating steps the article or semi-finished product may be transferred or placed into this further mould.

[0075] This further mould is mounted in a separate press different from the press having the heated surfaces, in particular this press has a pair of surfaces with a cooling system.

[0076] If the heating and pressing steps were carried out using a tray, the tray may be transferred into the first part of the cooled further mould.

[0077] Alternatively, the trays containing the articles or semi-finished products may be attached directly to the bottom of a press equipped with a cooling system and bonded together with punches of a further mould.

[0078] During the cooling and pressing step, the temperature of the preform or article is cooled from the heating temperature to room temperature, thus stabilizing the article or preform.

[0079] This cooling and pressing step is useful to complete the fabrication of articles and semi-finished products that must be given mechanical and structural properties.

[0080] At the end of the manufacturing process, preferably downstream of any cooling and pressurizing steps, both the articles and semi-finished products may be subjected to further processing steps to obtain the desired configuration of the finished article or semi-finished product.

[0081] For example, if the article is an end tip, side arm or front piece of an eyeglass frame, the further steps may include milling, bending and tumbling to remove sharp edges.

[0082] Advantageously, the articles and semi-finished products obtained by the method according to the invention may result in waste products that can be reused in the manufacturing method according to the invention.

[0083] Indeed, one of the advantages of the present invention lies in the fact that cellulose acetate maintains its mechanical and structural properties after the recovery and reuse process, in particular thanks to the specific operating conditions used, e.g., the working temperature.

[0084] The above description therefore highlights the advantages that can be obtained with the method according to the invention compared to conventional methods for the production of articles or semi-finished products made from cellulose acetate.

[0085] First, the method allows for the production of articles and semi-finished products from waste cellulose acetate, i.e., cellulose acetate obtained from previously produced cellulose acetate articles and / or semi-finished products.

[0086] Thus, as a result of this advantageous feature, the overall costs for manufacturing articles and semi-finished products can be substantially reduced and waste disposal processes can be avoided.

[0087] This advantageous feature also reduces warehouse inventory of materials and semi-finished products for manufacturing articles made from cellulose acetate.

[0088] Furthermore, the articles and semi-finished products thus obtained can have a variety of patterns and colors while maintaining the same structural and mechanical properties of articles made entirely from virgin cellulose acetate.

[0089] The manufacturing method according to the present invention allows the manufacture of articles made from waste using equipment and machines that are well known in the art, and therefore the implementation of the method does not require a dedicated plant.

[0090] Those skilled in the art can make changes to the above-described embodiments and / or replace the described elements with equivalent elements to meet their particular needs without departing from the scope of the appended claims.

Claims

1. 1. A method for producing an article or semi-finished product made from cellulose acetate, comprising: recovering waste consisting of cellulose acetate from previously manufactured articles and / or semi-manufactured articles; dispensing or placing a mixture of at least one polymeric material into a mold, said mixture being at least partially formed from said cellulose acetate waste material; heating the mixture inside the mold; pressing the mixture in the mold to form the article or workpiece; cooling or pressurizing the article or semi-finished product; Including, 10. A method according to claim 9, wherein the mixture is at least partially formed by waste fractions consisting of cellulose acetate.

2. 2. The method of claim 1, further comprising, upstream of the dispensing step, a step of crushing and / or grinding the waste material to obtain fragments of cellulose acetate.

3. 3. The method of claim 1 or 2, characterized in that the waste comprises shavings, shavings and cuttings resulting from the processing of semi-finished products for the manufacture of end tips, side arms and front pieces of cellulose acetate eyeglass frames, and the manufactured articles comprise end tips, side arms and front pieces of eyeglass frames, or wearable or everyday objects.

4. 3. The method of claim 2, wherein the waste comprises semi-finished products in the form of sheets or sheet pieces for manufacturing eyeglass frames.

5. 3. The method of claim 2, wherein said waste comprises end tips, front pieces and side arms of old eyeglass frames that must be disposed of.

6. 10. The method of claim 1, wherein the heating and pressurizing steps are performed simultaneously.

7. 7. The method according to claim 6, characterized in that the heating and pressing steps are carried out at a temperature value of 120°C to 170°C, in particular 140°C to 165°C, and at a pressure value of 10 bar to 120 bar for the pressing step, in particular 20 bar to 100 bar for the pressing step.

8. 10. The method of claim 1, wherein the dispensing or disposing step is performed with the mold open or unassembled and the mixture at room temperature.

9. 2. The method of claim 1, wherein the dispensing or placing step is carried out by dispensing the mixture in a tray, the tray being intended to be removably placed in the mold or to form part of the mold.

10. 10. The method of claim 1, wherein the cooling and pressurizing step, if present, is performed in a mold separate from and in addition to the mold in which the step for heating and pressurizing the mixture is performed.

11. 3. The method of claim 2, wherein the mixture is formed by combining the cellulose acetate fragments derived from waste with a polymeric material.

12. 12. The method of claim 11, wherein the polymeric material consists of virgin cellulose acetate in the form of granules and / or pieces.

13. 13. The method according to claim 12, characterized in that the mixture comprises waste fractions in a weight range of 50% to 95% by weight relative to the total weight of the mixture, preferably 70% to 95% by weight relative to the total weight of the mixture.

14. 3. The method according to claim 2, characterized in that the mixture is formed exclusively by cellulose acetate fragments derived from waste materials.

15. 3. The method according to claim 2, characterized in that the cellulose acetate fragments from the waste have different sizes and / or particle sizes and / or colours among themselves.