EP2621676B1

EP2621676B1 - Antistatic flexible abrasive with a combined support

Info

Publication number: EP2621676B1
Application number: EP11781617.3A
Authority: EP
Inventors: Michele Gottardelli
Original assignee: NAPOLEON ABRASIVES SpA
Current assignee: NAPOLEON ABRASIVES SpA
Priority date: 2010-09-30
Filing date: 2011-09-30
Publication date: 2015-09-30
Anticipated expiration: 2031-09-30
Also published as: EP2621676A1; PL2621676T3; ITVR20100190A1; ES2555408T3; SI2621676T1; RU2013113710A; BR112013006872A2; US20130309952A1; BR112013006872B1; IT1404101B1; US20180257198A1; HRP20151302T1; RU2583576C2; WO2012042505A1

Description

TECHNICAL FIELD

This invention concerns in general an antistatic flexible abrasive on a plastic film support used in the form of a tape.
More specifically, the invention refers to a flexible support made by using a combination of support material with a plastic film as its base.
The invention also refers to flexible abrasives made by using combined materials on a plastic support, to the production method of this combined support and to an established application of this flexible abrasive which uses this support.
The printed part of the plastic support can be treated with polymers or acids or electric systems (Corona system) or mechanical systems in order to increase the features of adhesion and mechanical friction.
This invention can be applied in the field of abrasives and in particular in the sector of flexible abrasives in tape form.

BACKGROUND ART

It is known that flexible abrasives have been used for a long time for the preparation of surfaces of various materials such as wood, metal, plastic, paint and composite materials.
In general, a flexible abrasive comprises a support element, a "maker coat" or also a layer of adhesive applied on the surface of the support, followed by the application of abrasive granules on the maker coat when it is still wet. The maker coat is the layer which, appropriately treated, allows the adhesion of the abrasive granules to the support.
A second layer of adhesive, known as a "size coat", is then usually applied on the maker coat and the adhesive layers are fully treated. The abrasive is then made flexible to break the rigid adhesive layers and produce a suitably flexible abrasive product.
The flexible abrasive is subsequently transformed into various abrasive products such as sheets, discs, tapes, etc., according to the particular use of the flexible abrasive, the specific components of the abrasive, the product to be processed and the way in which it is carried out.
The traditional support used in the production of the flexible abrasive can be made of various materials, depending on the application of the flexible abrasive, for example paper, fabric, plastic (polyester film).
In the case of fabric, the support can, for example, be a woven or "stitch-bonded" fabric such as rayon, cotton, nylon, polyester or mixed fabrics.
It is commonly known that the printed side of conventional products such as paper, fabric, non-woven materials, and combined paper/fabric supports are characterised by considerable roughness, and that the degree of this roughness depends on the type of support used.
This roughness in the use of the flexible abrasive converted to tape form is in proportion to the degree of friction necessary in the use of automatic and semi-automatic machines.
This proportion is greater when the abrasive granule is a macrogranule. In particular in abrasive grains from P120 to P16.
A first drawback is encountered with the use of conventional abrasives on plastic film in tape form. In the traditional forms of production of flexible abrasives on plastic film support, if the roughness of the printed surface side of the plastic film is not sufficient, the abrasive support can not be used on automatic or semi-automatic machines in the form of narrow or wide tapes due to slipping.
Another drawback encountered with flexible abrasives with plastic film support in the form of narrow or wide tapes is the poor pliability of the support, in the sense of its ability to absorb the roughness, thus not allowing the typical shock-absorber effect that the previously mentioned conventional supports have. This effect is more evident with fine grains, usually required in finishing applications.
This shortcoming is particularly evident in the use of abrasive tapes on painted surfaces in which micrograins are required for precision finishing.
Another important problem is the dissipation of the heat generated by the friction of the tapes during polishing with automatic and/or semi-automatic machines. This problem is particularly evident in the finishing of glossy furniture with polyester and polyurethane-based paints.
If these paints are not perfectly catalysed, their thermoplastic property will emerge when the temperature rises, leading to a premature clogging of the abrasive tape, which can also occur with plastic materials, marble finishing, and sanding of resins and paints of ferrous and non-ferrous materials.
An additional problem that characterises the application of only flexible abrasive on plastic film support in the form of abrasive tapes is the high degree of electrostatic that can accumulate on the plastic support. The antistatic property is extremely important in the wood and painting sectors, where the electrostatic charge that accumulates on the supports can generate sparks. In certain conditions, these sparks can cause the ignition of polishing dust and of suction systems.
In general, the use of a tape that provides a better performance would be useful in the production of furniture, plastic materials, marble finishing, sanding of resins and paints of ferrous and non-ferrous materials with abrasive tapes, not only for the lower consumption of tapes but also because the operator would have to change the abrasive tapes less often and daily production would thus be higher.
Document US 2007/0011951 A1 discloses an abrasive product including a plurality of abrasive particles and a resin cured with a polythiol group. A methof of preparing the abrasive product includes contacting the plurality of abrasive particles with a curable composition that includes a resin and a polythiol group, and curing the curable composition to produce the abrasive product.

DESCRIPTION OF THE INVENTION

This invention proposes to provide a new support for the production of flexible abrasives, with improved yield and performance for the tape sanding of furniture, plastic materials, marble finishing, and sanding of resins and paints of ferrous and non-ferrous materials.
The products created according to the invention concern a flexible abrasive for sanding applications, in the form of tapes that have greater resistance to clogging, better finishing, better resistance to tensile stress, better antistatic features, and better dissipation of heat with respect to the traditional abrasives used to date.
This will make it possible to eliminate or at least reduce the drawbacks indicated above.
This is achieved by means of a flexible abrasive in tape form the features of which are described in the main claim.
The dependent claims of the solution in question describe advantageous embodiments of the invention.
This invention foresees that the coated flexible abrasive consists of a layer of abrasive-containing resins, a support plastic film layer and a reinforcement substratum of paper which satisfies the following requirements: it is economical, resistance to tensile stress, can absorb shocks, dissipates heat easily, is extremely antistatic and has sufficient friction for use in automatic and semi-automatic machines.
This type of flexible abrasive on a combined support according to the invention allows easier and practical handling and installation in automatic and semi-automatic machines.
The resulting flexible abrasive has greater mechanical resistance to tensile stress, greater heat dissipation, less tendency to clog, greater shock-absorbance, better finishing, and greater antistatic ability than a product with just film or traditional abrasives (paper, fabric, combined paper-fabric, non-woven, etc.).
According to an important feature of the invention, the antistatic process (with the addition of graphite, mineral salts, and more in general of substances that allow ion exchange) is carried out at the same time as lamination of the support while, according to background art, in some specific applications an antistatic product is added to the resin with which the abrasive is bound or coated.
On the other hand, background art does not foresee making the support, and thus the end product, antistatic during the production process, using glues with antistatic properties obtained with the addition of graphite, carbon black, metal salts and more in general substances that allow ion exchange.
As mentioned previously, the antistatic feature of abrasive tapes is extremely important for some fundamental reasons

Safety aspects

1) Abrasive film do not generally have marked antistatic properties as they are mainly used in disc form (there is no way of accumulating high charges in this format due to its size).
2) When an abrasive tape is produced with plastic film (without any treatment or additional support) electrostatic charge accumulates.
3) the electrostatic charge that accumulates on the tape can sometimes reach high enough values to generate electric sparks.
4) When plastic film tapes are used on solvent-based or more generally inflammable paints, these electrical discharges are extremely dangerous.
5) The fine dust that is produced by the sanding of solvent-based or more generally inflammable paints is collected in the aspiration ducts of the polishing machines and deposited in appropriate containers.
6) When an electrical discharge occurs (due to the static charge on the abrasive tape) in an environment that is full of inflammable dust (aspiration ducts or dust containers), the possibility of fire is very high.

Finishing aspects

a) The electrostatic charge that accumulates on the items to be sanded or on the abrasive tape means that the dust present in the environment is attracted to it.
b) When the dust is attracted to the sanded item, it becomes more difficult to remove. During the painting operations following the sanding, defects can arise due to the dust "attracted by the surface".
c) When the dust is attracted by the abrasive tape, it deposits on the surface of the tape. This speeds up the deterioration of the tape due to a phenomenon known as clogging.

The antistatic properties of the abrasive tape according to the invention are therefore achieved as follows:

A) By means of a surface treatment of the polyester film;
B) By means of a resin with antistatic properties;
C) By means of a second antistatic support, applied using an antistatic binder.

When one of these three properties is missing, the completely anti-electrostatic feature of the tape is lost.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become clear on reading the description given below of one embodiment, provided as a non-binding example, with the help of the accompanying drawings, in which:

figure 1 represents a schematic diagram of the production of the flexible abrasive on a combined support by means of lamination;
Figure 2 represents a cross-section of the flexible abrasive on a combined plastic film support and base support.
Figure 3 represents a schematic diagram of the production of the flexible abrasive on a combined support according to the conventional method, that is to say starting from a laminated support;
Figure 4 represents a schematic diagram of the production of the flexible abrasive on a combined support by means of lamination in line after preparation of abrasive according to the conventional method.

DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

Reference is initially made to figure 2 which shows a cross-section of the flexible abrasive on a combined plastic film support and base support.
According to the invention, the flexible abrasive on a combined support indicated overall with the reference number 10 comprises the combination, obtained in various ways, of a flexible abrasive on plastic film 11, comprising binding resins 8, with a base support or substratum 12 made of paper.
More specifically, the combined plastic film/substratum indicated with reference number 9 consists of the layered combination of the following materials: a layer of plastic film 13, a base support or substratum 12 made of paper and a layer of adhesive material 18, such as glue or the like.
The flexible abrasive on plastic film (11) in tape form according to a form of embodiment of the present invention consists of: a layer of plastic film 13, a first intermediate binder layer or Maker Coat 14, a second binder layer or Size Coat 15 which holds the layer of abrasive grains 16, and finally a third binder layer or Supersize Coat 17.
According to the invention, the flexible abrasive on plastic film 11 is combined with the base support or substratum 12 made of paper, the base or substratum 12 being fixed to the plastic film 13 by means of a layer of adhesive material 18, such as glue or the like.
The above is achieved by means of a continuous lamination process, and figure 1 shows an example of the creation of the flexible abrasive on a combined plastic film - substratum support by means of lamination.
With reference to figure 1, the plant that allows the aforesaid lamination process indicated overall with 19 comprises a reel 20 of flexible abrasive on plastic film 21 which is transferred to a lamination cylinder 22 positioned in contact with an additional lamination cylinder 23 which receives the sheet of support material 24 from a reel 25. A container 26 of glue 27 is positioned between the two cylinders.
The laminated film 28 exiting from the two cylinders 22 and 23 can pass through a drying oven 29 before being wound on a reel 30.
The preparation, of the flexible abrasive with a combined plastic, film support and paper base support for abrasive tapes can be carried out by applying the maker coat, abrasive and size coat to a combined support consisting of plastic film and paper and this application can be achieved in a direct fashion in two different ways:

1) Creation of the flexible abrasive on a combined support (plastic film - substratum) by on-line lamination before the preparation of the abrasive according to the traditional method (fig.3), and according to this method the combined support is laminated on-line and then coated with the maker coat, abrasive grains, size coat and third layer;
2) Creation of the flexible abrasive on a combined support (plastic film - substratum) by on-line lamination after the preparation of the abrasive according to the traditional method (fig.4), and according to this method the substratum is laminated on-line after the plastic film has been coated with the maker coat, abrasive grains, size coat and third layer.

Figure 3 shows a plant suitable for the creation of the flexible abrasive on a combined support (plastic film - substratum) by on-line lamination before the preparation of the abrasive according to the traditional method.
This system optimizes production costs thanks to the continuous lamination and production of the abrasive process on the plastic film side.
The working cycle of the lamination unit 31 shown in figure 3 comprises the presence of a reel of plastic film 32 and a reel of support base material 33 made of paper. These materials are laminated with the glue by means of the lamination cylinders 34 and 35 and the combined plastic film - paper base support moves on to the abrasive process stage. The parts of the plant necessary for this process are listed below:

- The film passes through the printing area 36, where the combined support is printed on the support side with the distinctive features of the product being processed.
- The film passes through the first binder - Maker coat 37, where a binder, which can be an animal glue, a ureic glue, a phenolic glue, an epoxy glue or any type of resin or glue that can be used to create adhesion of the abrasive to the plastic support, is deposited on the combined support.
The sector 38 ensures that the abrasive is deposited on the combined support on which the first binder is still wet. The first binder must not be completely dry or catalysed in order to allow the adhesion of the grains. The abrasive is intended in a broad sense since it can be aluminium oxide, silicon carbide, zirconium, ceramic, diamond, titanium carbides or oxides or a mixture of any of the former including any other type of material that can be used as an abrasive.
- The film passes through a first oven 39 which dries and cures the first binder, allowing the the abrasive grains to grip the combined support. The required temperature depends on the type of binder used and can vary from 40°C to 130°C. The time needed in the oven varies according to the type of grain and resin used, varying from a minimum of 1 minute to a maximum of 2 hours.
- The film now passes through the second binder - Size coat 40, where, once the first resin is dry, the product (consisting of the combined support, the first binder and the abrasive grains) is coated with a fixing binder or size coat, which in turn can be an animal glue, a ureic glue, or a phenolic glue, etc., depending on what the product will be used for. This binder is deposited on the product by means of rubber rollers, by air, spray or other systems. This resin coating can contain fillers such as calcium or potassium carbonate, iron.oxides, dyes, stearates, and any other substance that can have a technical value for the use of the product or the economic property of the product.
- Once the second binder has been applied, the product enters the second oven 41 for curing. The required temperature depends on the type of binder used and can vary from 40°C to 130°C. The time needed in the oven varies according to the type of grain and resin used, varying from a minimum of 1 minute to a maximum of 2 hours.
- At the end of the process the product is wound on the finished reel 42 and, depending on the binders used, can be used as it is or transferred to post-curing ovens for perfect catalyzing of the binders before the product is used.

Figure 4 shows a plant suitable for the creation of the flexible abrasive on a combined support (plastic film substratum) by on-line lamination after the preparation of the abrasive on plastic film according to the traditional method.
This system optimizes production costs thanks to the continuous lamination and production of the abrasive process on the plastic film side.
The cycle begins from a reel of plastic film 43 positioned on an unwinder at the start of the plant, from which the film passes through a printer 44 for printing on the support side with the distinctive features of the product being processed.
The film passes through the first binder - Maker coat 45. A binder, which can be an animal glue, a ureic glue, a phenolic glue, an epoxy glue or any type of resin or glue that can be used to create adhesion of the abrasive to the plastic support, is deposited on the combined support.
The film now passes through the sector 46 where the abrasive is deposited while the first binder is still wet. The first binder must not be completely dry or catalysed in order to allow the adhesion of the grains. In this case too, the abrasive is intended in a broad sense since it can be aluminium oxide, silicon carbide, zirconium, ceramic, diamond, titanium carbides or oxides or a mixture of any of the former including any other type of material that can be used as an abrasive.
The film passes through a first oven 47 which dries and cures the first binder, allowing the the abrasive grains to grip the plastic film by means of the second binder - Size coat 48, and through the second oven 49 for curing.
At this point, that is to say once the flexible abrasive on the plastic film is ready, lamination of the abrasive to the paper substratum takes place.
Similar to the previous cases, these materials are laminated in the lamination unit 50 by means of lamination cylinders using glue. The combined plastic film - base support made of paper is wound on a reel 51 and, if necessary, passed through a drying oven 52.
According to the invention, the main components of the combined plastic film/paper abrasive (that is to say the abrasive film and the paper support) have antistatic properties.
In addition, to allow the combination of the main components to also be antistatic, the glue used for the lamination also has antistatic properties.
Therefore, according to the invention, carbon black, graphite, metal salts or similar are added to the binding resins (make coat and size coat) for plastic film abrasives.
This ensures an abrasive film with antistatic properties.
As far as the paper support is concerned, carbon black, graphite, metal salts or similar are added to the paper pulp when the paper is produced, thus guaranteeing that the paper is antistatic.
In addition, to ensure that the combination of abrasive film and paper support is also antistatic, an adhesive or glue with antistatic properties is use in the lamination step according to the invention. In particular, carbon black, graphite, metal salts or similar are added to the glue (whether it is vinyl, polyurethane or another type) to allow movement of the electric charges.
The abrasive tape according to the invention is thus completely antistatic, achieving the predefined aims.

APPLICATION EXAMPLES

The following non-binding examples further describe the invention. All the measurements described in the following examples respect the international system.

Table 1: TYPE OF MATERIALS used in the test

Name	Detailed Description
Paper	Paper Support weight A (80g/m2) supplied by Arjo Wiggins or Kimberly Clark or other suppliers.
Adhesive	Bicomponent adhesive supplied by Concorde Adesivi Italy
Abrasive Film	Abrasive on film support type GF02 supplied by Naploen Abrasives

TEST CONDITIONS AND PARAMETERS:

Type of abrasive tapes: Abrasive tape with combined support produced by laminating Abrasive Film and Paper
Tape dimensions and grain:

150mm x 9450mm grain, P1000, P1200 and P1500
Type of join: Head to head join
Automatic machine: Nerli.
Operating parameters: Minimum speed 1.5 m/s, Max 9 m/s. Minimum pressure 1 bar, Maximum pressure 4 bars.
Type of laminar tape: Felt

Table 2: FRICTION

Test to evaluate the increase of friction due to the combined substratum-plastic film support.
Type of Support:	Min. speed	Max. speed	Min. pressure	Max. pressure	Stop
Paper	1.5	9	1 bar	4 bars	No
Film	1.5	7.6	1 bar	1.8 bars	YES

The test was carried out using a Nerli semi-automatic machine. The objective was to evaluate the working conditions to discover why the abrasive tape with different supports stopped when the speed and pressure changed. The halt of the abrasive tape shows that the friction of the "abrasive film - piece being processed" is greater than the friction of the "support - movement pulleys".

The data reported in table 2 show that a tape of flexible abrasive, consisting only of abrasive plastic film, reaches lower values of speed and pressure than the film-paper one. The abrasive consisting of a combined support reaches the limit working conditions of the machine (minimum/maximum pressure, minimum/maximum speed) without stopping.

Table 3: FINISH

Test to evaluate the improved finish due to the combined substratum-plastic film support.
Type of Abrasive:	Finish Obtained (Ra)	Notes
Paper - Film	0.51
Film only	0.54
Traditional Abrasive	0.65	Rapidly decays

The piece to be sanded (same size and type of paint) and the conditions (same machine speed and pressure) being the same, the grain of the tapes being the same, the finish of the pieces sanded with the abrasive on a laminated support is better. The constancy of the roughness obtained with the products on a laminated support is also markedly superior (approx. 1.7:1).

Table 4: CLOGGING

Test to evaluate the greater duration (less tendency to clog) due to the combined substratum-plastic film support with respect to a traditional abrasive and to a simple film abrasive.
Type of Abrasive:	Number of pieces	Notes
Paper - Film	7
Film only	6
Traditional Abrasive	4	Finish at the 4th piece very low

The piece to be sanded (same size and type of paint) and the conditions (same machine speed and pressure) being the same, the grain of the tapes being the same, the life of the abrasive on a combined film support is much longer than that of traditional abrasives (abrasive currently used in the process).

Table 5: INSTALLATION

Test to evaluate the easier handling (easier installation) due to the combined substratum-plastic film support with respect to a traditional abrasive and to a simple film abrasive.
Type of Abrasive:	Installation time (sec)	Notes
Paper - Film	45 sec	Standard time
Film	55 sec
Traditional Abrasive	45 sec	Standard time

The working conditions being the same, the tapes produced with a laminated support have similar installation times to traditional abrasives, while those produced using only unsupported plastic film require a slightly higher handling time.
The products used also have the marked antistatic features of traditional abrasives, but guarantee a markedly better finish and resistance to clogging. The antistatic property is extremely important in the wood and painting sectors, where the electrostatic charge that accumulates on the supports can generate sparks. In certain conditions, these sparks can cause the ignition of polishing dust and of suction systems.
This invention foresees that the flexible abrasive with combined support consists of a layer of abrasive-containing resins, a support plastic film layer associated with a reinforcement substratum of paper which satisfies the following requirements: it is economical, resistant to tensile stress, can absorb shocks, dissipates heat easily, is extremely antistatic and has sufficient friction for use in automatic and semi-automatic machines.
The product obtained allows easier and practical handling and installation in automatic and semi-automatic sanding machines.
The resulting flexible abrasive has greater mechanical resistance to tensile stress, greater heat dissipation, less tendency to clog, greater shock-absorbance, better finishing, and excellent antistatic properties compared to a product with just film or traditional abrasives (paper, fabric, combined paper-fabric, non-woven, etc.).
The invention is described above with reference to a preferred embodiment. It is nevertheless clear that the invention is susceptible to numerous variations in the framework of the appended claims.

Claims

A flexible and antistatic abrasive in tape form (10) comprising a plastic film support (13) coated with binding resins (8), consisting of a first layer of resin or "maker coat" (14), abrasive in granules (16) fixed by a second layer of resin or "size coat" (15) whereby:
- said plastic film support (13) is provided of an antistatic surface treatment, whereby both the maker coat (14) and the size coat (15) binder resins contain carbon black, graphite, metal salts or similar antistatic agents, whereby said plastic film support;

- said flexible and antistatic abrasive in tape form further comprises a reinforcement substratum constituted by a base support (12) that is made of paper;
characterised in that

- said base support (12) contains carbon black, graphite, metal salts or similar antistatic agents; and

- said plastic film support (13) and said base support (12) are joined together through a lamination process by means of a suitable adhesive or glue containing carbon black, graphite, metal salts or similar antistatic agents.
A flexible and antistatic abrasive in tape form (10) according to claim 1, characterised in that said plastic film support (13) is further coated with a third layer or "supersize coat" of resin containing carbon black, graphite, metal salts or similar antistatic agents.
A flexible and antistatic abrasive in tape form (10) according to any one of the preceding claims, characterised in that said plastic film is a polyester film.
A flexible and antistatic abrasive in tape form (10) according to any one of the preceding claims, characterised in that said adhesive or glue is either a vinyl or polyurethane glue.