CN1315951C - Laser Absorbing Additives - Google Patents

Abstract

A laser light absorbing additive comprising particles comprising at least a first polymer having a first functional group and 0 to 95wt% of an absorber, the weight percentage being relative to the total amount of the first polymer and the absorber, the first polymer being bound in at least part of the particle surface by the first functional group being bound to a second functional group, the second functional group being bound to a second polymer.

Description

Laser Absorbing Additives

The invention relates to a laser absorbing additive.

Such an additive is known from WO 01/0719, in which antimony trioxide with a particle size of at least 0.5 μm is used as absorbent. The additive is applied in the polymer composition in such an amount that the composition comprises at least 0.1 wt.% of the additive, thereby enabling the application of a dark marking against the light background of the composition. Preferably, pearlescent pigments are also added for better contrast.

Known additives have the disadvantage that in many cases, especially in compositions with polymers which themselves are only weakly carbonized, only poor contrast can be achieved by laser irradiation.

It is an object of the present invention to provide an additive which, when likewise mixed into a polymer which is itself only weakly carbonized, produces a composition which can be written with a laser with good contrast.

This object is achieved according to the invention: said additive comprises particles comprising at least a first polymer having a first functional group and 0 to 95 wt.% of an absorbent, said weight percentage being relative to said first polymer and the absorbent, and in at least a portion of the surface of the particle, the first polymer is bound to a second functional group bound to a second polymer through the first functional group.

When irradiated with laser light, it was found that the polymer composition comprising the additive according to the invention produces an unexpectedly high contrast between irradiated and non-irradiated parts. This contrast ratio is also significantly higher than when a composition comprising only the absorbent and the first polymer or the second polymer is applied.

The additive according to the invention contains 0 to 95 wt.% of absorbent. Surprisingly, it has been found that an additive consisting of particles of a first polymer surrounded by a layer of a second polymer bonded thereto, which does not contain a separate absorber, provides, under the action of a laser, Its own obviously higher blackening effect.

However, it is preferred that the additive comprises at least 1 wt% or more, preferably at least 2, 3, 4, 5 or 10 wt%, of absorber, as this leads to more rapid blackening in the additive when irradiated with a laser. The additive contains up to 95% by weight of absorbent. At higher percentages, the black forming ability tends to decrease, probably because relatively low amounts of the second polymer, especially the first polymer, are present in the additive, and the presence of these components in the additive has been found to be important in the present invention. Compositions are critical as they appear to promote carbonation as explained later. Preferably, the additive comprises between 5% and 80% by weight of absorbent. In this range, the composition exhibits the best black forming ability.

As the absorber, those substances capable of absorbing laser light of a certain wavelength can be used. In practice, this wavelength is between 157nm and 10.6μm, which is the conventional wavelength range for lasers. The use of other absorbers in the additive according to the invention is also conceivable if lasers with longer or smaller wavelengths can be used. Examples of such lasers operating in said region are CO ₂ lasers (10.6 μm), Nd:YAG lasers (1064, 532, 355, 266 nm) and excimer lasers of the following wavelengths: F ₂ (157 nm), ArF (193nm), KrCl (222nm), KrF (248nm), XeCl (308nm) and XeF (351nm). Preference is given to using Nd:YAG lasers and _CO2 lasers, since these types of lasers operate in a wavelength range which is very suitable for inducing thermal processes for marking. Such absorbers are known per se, as is the wavelength range in which they can absorb laser radiation. Various substances which can be considered as absorbents are described below.

The activity of the additives, preferably mixed into the polymer in the form of particle sizes between 200 nm and 50 μm, appears to be based on the transfer of energy absorbed from the laser light to the polymer. The polymer can decompose due to this heat release, leaving carbon behind. This process is called carbonization. The amount of carbon remaining depends on the polymer. In additives according to the prior art, the heat released to the environment in many cases does not appear to be sufficient to produce acceptable contrast, especially in the case of weakly carbonized polymers which, on decomposition, leave very little carbon.

Examples of suitable absorbents are oxides, hydroxides, sulfides, sulfates and phosphates of metals such as copper, bismuth, tin, aluminium, zinc, silver, titanium, antimony, magnesium, iron, nickel and chromium, and laser absorbing (inorganic) organic dyes. Particularly suitable are antimony trioxide, tin dioxide, barium titanate, titanium dioxide, aluminum oxide, copper phosphate and anthraquinone as well as azo dyes.

The additive according to the invention essentially consists of particles comprising a first polymer having a first functional group and 0 to 95% by weight, preferably 1 to 95% by weight and more preferably 5 to 80% by weight of an absorbent mixed therein . This weight percent is relative to the total amount of first polymer and absorbent. This first polymer is preferably polar so that it can adhere by some force to the usually inorganic absorbent, which is also usually polar. This ensures that the absorber does not migrate to other components of the composition (discussed below) during processing of the additive in which the additive is used as a laser absorbing component.

The size of the additive particles is practically between 0.2 and 50 μm. For efficient laser light absorption, the size of these particles is preferably equal to at least about twice the wavelength of the laser light to be subsequently applied. As an additive particle, it is considered in this respect a certain amount of absorbent (according to the size of the absorbent particle consisting of single or multiple absorbent particles), together with a certain amount of the Particles are separated from the first polymer. Particle size is understood to be the largest dimension in any direction, thus, for example, the diameter of spherical particles and the largest length of ellipsoidal particles. Particle sizes greater than twice the laser wavelength undoubtedly lead to a lower efficiency of laser absorption, but also have less impact on the decrease in transparency due to the presence of additive particles. This size is preferably between 500 nm and 2.5 μm.

The absorbent is present in the additive in the form of particles smaller than the particle size of the additive. The lower limit of the particle size of the absorbent is determined by the requirement that the absorbent must be able to be mixed into the first polymer. Those skilled in the art know that this miscibility is determined by the total surface of the absorbent particles for a given weight, and when knowing the desired size of the additive particles and the desired amount of absorbent to be mixed in, the skilled person will The lower limit of the particle size of the absorbent to be mixed can be easily determined. Generally, the _D50 of the absorber particles will be not less than 100 nm, and preferably not less than 500 nm. In the additive according to the present invention, in at least a part of the particle surface, the first polymer is bonded to the second functional group bonded to the second polymer through the first functional group.

Both the first and second polymers are preferably thermoplastic polymers, as this will facilitate the incorporation of absorbers into the first polymer and additives into the base polymer to make it suitable for laser writing, respectively.

The first polymer comprises a first functional group and through this group it is bound to a second functional group bound to the second polymer. Thus, around the surface of the additive particle there is a layer of second polymer bonded to the first polymer via respective functional groups, which at least partially isolates the first polymer in the particle from the environment surrounding the additive particle. The thickness of this second polymer layer is not critical and is generally negligible with respect to the particle size and amounts for example between 1 and 10% thereof. For the second polymer grafted with eg 1 wt% MA, the amount of the second polymer relative to the first polymer is eg between 2 and 50 wt%, and preferably less than 30 wt%. For other functional groups and/or other percentages of second functional groups, the amount of second polymer should be selected such that the amount of second functional groups is present corresponding to a given instance. As the number of secondary functional groups increases, the size of the additive particles is found to decrease.

In addition to the second polymer bonded to the first polymer there is preferably also an amount of a third polymer not provided with functional groups, such as a polyolefin. It is also possible to choose a base polymer into which the masterbatch is later mixed as a third polymer. If desired, this base polymer can also be added as a fourth polymer, which will later improve incorporation into larger amounts of base polymer. This is the case, for example, when silicone rubber is used as matrix polymer. This non-functionalized third polymer may be identical to the bound second polymer, but must at least be compatible therewith, in particular miscible. Thus, said isolation of the first polymer in the particle from the environment is improved and also the mixing of the additive according to the invention into the matrix polymer to make it laser writeable, wherein in this case the The additives described above can be considered as additive masterbatches in the non-functionalized third polymer. In this masterbatch, the proportion of the functionalized second polymer plus the non-functionalized third polymer is preferably between 20 and 60% by weight of the total amount of the first, second and third polymer and absorbent. More preferably, this proportion is between 25 and 50 wt%. In said range, a masterbatch is obtained which can be suitably incorporated by melt processing. Higher proportions than said 60% are permissible, but in this case the amount of additive particles suitable in the masterbatch is relatively small.

As the first and second functional groups, any two functional groups capable of reacting with each other can be considered. Examples of suitable functional groups are carboxylic acid groups and their ester groups and anhydride and salt forms, epoxy rings, amine groups, alkoxysilyl groups or alcohol groups. As is known to those skilled in the art, such functional groups can be combined in a reactive manner with each other. The functional groups may be present in the first and second polymers themselves, such as terminal carboxylic acid groups in polyamides, but may also be present, for example, by grafting as commonly used to provide functional groups to, for example, polyolefins (e.g., to obtain Known polyethylene grafted with maleic acid) has been applied to the first and second polymers.

Suitable first polymers are semi-crystalline or amorphous polymers comprising first functional groups which are reactive in the melt with second functional groups of the second polymer.

The respective melting point and glass transition temperature of the semi-crystalline polymer and amorphous polymer are preferably above 120°C and above 100°C, respectively, and more preferably above 150°C and above 120°C, respectively. Suitable second functional groups are, for example, hydroxyl groups, phenolic groups, (carboxylic) acid (anhydride) groups, amine groups, epoxy groups and isocyanate groups. Examples of suitable second polymers are polybutylene terephthalate (PBT), polyethylene terephthalate (PET), amine functionalized polymers including for example polyamide-6, polyamide-66 , semicrystalline polyamides of polyamide-46 and amorphous polyamides such as polyamide-61 or polyamide-6T, polysulfones, polycarbonates, epoxy-functionalized polymethyl(meth)acrylates, Styrene acrylonitrile functionalized with oxygen or other functional groups as described above. Suitable first polymers are those of usual intrinsic viscosity and molecular weight. For polyesters, the intrinsic viscosity is, for example, between 1.8 and 2.5 dl/g, measured in m-cresol at 25°C. For polyamides, the molecular weight is for example between 5,000 and 50,000.

For the selection of a suitable first polymer, the person skilled in the art will in principle be guided by the desired degree of adhesion of the first polymer to the absorbent and its required degree of carbonization. Most preferably, this adhesion of the first polymer to the absorbent is superior to the adhesion of the second and third polymers (to be defined later) to the absorbent. This ensures the integrity of the absorbent additive during its processing. It is also desirable that the absorbent and the first polymer cannot chemically react with one another. This chemical reaction causes degradation of the absorbent and/or the first polymer, leading to undesired by-products, discoloration and poor mechanical and marking properties.

The first polymer preferably has a degree of carbonization, defined as the relative amount of carbon remaining after pyrolysis of the polymer in a nitrogen atmosphere, of at least 5%. At lower degrees of carbonization, the contrast obtained upon laser irradiation decreases, and at higher degrees of carbonization, the contrast increases until saturation occurs. Surprisingly, the presence in the additive according to the invention of a polymer with such a low degree of carbonization, which itself hardly produces a visible contrast, already makes it possible to obtain a high contrast during laser irradiation as a compatibilizing polymer . Polyamides and polyesters are well suited due to their availability in a wide range of melting points and have degrees of carbonization of approximately 6% and 12%, respectively. Polycarbonate is a good fit, in part due to its 25% higher degree of carbonation. Furthermore, both polyamides and polycarbonates appear to exhibit good adhesion to most inorganic absorbents, especially alumina and titania. Polyamides also exhibit good adhesion to antimony trioxide. Furthermore, the reaction of their first reactive groups with, for example, MA graft polymers (discussed later) which may advantageously be used as graft polymers, is irreversible under the conditions in which the additives are normally used.

Suitable as the second polymer are thermoplastic polymers having functional groups which can react with the first functional groups of the first polymer to be applied. Particularly suitable as the second polymer are polyolefin polymers grafted with ethylenically unsaturated functional compounds. The ethylenically unsaturated functional compound grafted onto the polyolefin polymer can react with the first functional groups of the first polymer, for example with the end groups of the polyamide. Polyolefin polymers which may be considered for use in compositions according to the invention are those which may be grafted with ethylenically unsaturated functional compounds, or which may incorporate functional compounds into the polymer chain during polymerization. Homopolymerization and copolymerization of one or more olefin monomers. Examples of suitable polyolefin polymers are ethylene polymers, propylene polymers. Examples of suitable ethylene polymers are all thermoplastic homopolymers of ethylene and ethylene with as comonomers one or more alpha-olefins having 3 to 10 carbon atoms (in particular propylene, isobutene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene) which can be prepared using known catalysts such as Ziegler-Natta, Phillips and metallocene catalysts. The amount of comonomer is generally between 0 and 50 wt.%, preferably between 5 and 35 wt.%. Such polyethylene is known by names such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and linear very low-density polyethylene (VL(L)DPE). Suitable polyethylenes have densities between 860 and 970 kg/ ^m3 . Examples of suitable polypropylene polymers are homopolymers of propylene and copolymers of propylene and ethylene, wherein the proportion of ethylene is at most 30 wt.%, preferably at most 25 wt.%. Their melt flow index (230° C., 2.16 kg) is between 0.5 and 25 g/10 min, more preferably between 1.0 and 10 g/10 min. Suitable ethylenically unsaturated functional compounds are those graftable on at least one of the aforementioned suitable polyolefin polymers. These compounds contain carbon-carbon double bonds and can form side chains on polyolefin polymers by grafting them. These compounds can be provided in a known manner with one of the functional groups mentioned above as suitable examples.

Examples of suitable ethylenically unsaturated functional compounds are unsaturated carboxylic acids and their esters, anhydrides and metal or metalloid salts. Preferably, the ethylenically unsaturated bond in the compound is conjugated to the carbonyl group. Examples are acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, methyl crotonic acid and cinnamic acid and their esters, anhydrides and possible salts. Among the compounds having at least one carbonyl group, maleic anhydride is preferred.

Examples of suitable ethylenically unsaturated functional compounds having at least one epoxy ring are, for example, glycidyl esters of unsaturated carboxylic acids, glycidyl ethers of unsaturated alcohols and alkylphenols, and vinyl esters of epoxy carboxylic acids and allyl esters. Glycidyl methacrylate is particularly suitable.

Examples of suitable ethylenically unsaturated functionalized compounds having at least one amine functionality are amine compounds having at least one ethylenically unsaturated group, such as allylamine, propenyl, butenyl, pentenyl and hexenylamines, such as the amine ethers of isopropenylphenylethylamine ether. The amine groups and unsaturated bonds are positioned relative to each other such that they do not interfere with the grafting reaction to any undesired extent. Amines can be unsubstituted, but can also be substituted by, for example, alkyl and aryl groups, halogens, ether groups and thioether groups.

Examples of suitable ethylenically unsaturated functionalized compounds having at least one alcohol functionality are all compounds having hydroxyl groups which may or may not be etherified or esterified and ethylenically unsaturated compounds such as ethanol and higher Allyl and vinyl ethers of alcohols such as branched and unbranched alkyl alcohols, and allyl and vinyl esters of alcohol-substituted acids, preferably carboxylic acids and _C3 - _C8 enols. Furthermore, the alcohols may be substituted by, for example, alkyl and aryl groups, halogens, ether groups and thioether groups without this affecting the grafting reaction to any undesired extent.

Examples of oxazoline compounds suitable as ethylenically unsaturated functionalized compounds in the context of the invention are, for example, those compounds of the general formula:

Wherein, each R independently of another hydrogen is halogen, C ₁ -C ₁₀ alkyl or C ₆ -C ₁₄ aryl.

The amount of ethylenically unsaturated functionalized compound in the polyolefin polymer functionalized by grafting is preferably between 0.05 and 1 mg equivalent per gram of polyolefin polymer.

As third polymers there come into consideration the same polymers as those mentioned above for the second polymer, however in their non-functionalized form.

The second polymer, especially the third polymer, may contain pigments, colorants and dyes. This has the advantage that, where colored compositions are preferred, it is not necessary to add a separate colored masterbatch when mixing the laser-writable additive with the matrix polymer.

The invention also relates to a method of preparing an additive according to the invention, comprising mixing a first polymer comprising an absorbent and having first functional groups with a second polymer comprising second functional groups reactive with the first functional groups.

It has been found that in this way the additive is divided into particles which consist of a mixture of the first polymer and the absorbent and which are provided on their surface with a layer of the second polymer so that after mixing the additive into the matrix polymer Thereafter, optimum contrast is obtained within it when laser writing is performed.

The composition comprising the absorbent and the first polymer can be prepared by mixing melts of the absorbent and the first polymer. The ratio between the amount of the first polymer and the amount of absorbent in the composition is between 90 vol.%: 10 vol.% and 60 vol.%: 40 vol.%. More preferably, this ratio is between 80 vol.%:20 vol.% and 50 vol.%:50 vol.%.

The composition is mixed with a second polymer comprising a second functional group reactive with the first functional group. This mixing takes place above the melting points of the first and second polymers, and preferably in the presence of an amount of a non-functionalized third polymer. Third polymers that come into consideration are in particular those polymers already mentioned above as second polymers, but in their non-functionalized form. This third polymer need not be the same as the functionalized second polymer. The presence of the non-functionalized third polymer ensures sufficient melt processability of the overall mixture to obtain the desired uniform distribution of additive particles in the resulting masterbatch.

In the melt, the functional groups react with each other and a barrier layer of the second polymer forms on at least part of the surface of the additive particle. At some point, the sequestering effect of the second polymer will become dominant, and any unreacted first polymer present in the additive particles will no longer be able to pass into the surrounding melt. This isolation effect is more effective when the polarity difference between the first and second polymers is greater. In the above, it has been pointed out that the first polymer preferably has polarity. It is also preferred that the second and third polymers are less polar than the first polymer, and more preferably that the second and third polymers are completely or almost completely non-polar.

The size of the additive particles in the resulting masterbatch depends on the amount of second functional groups. The upper and lower limits within which to obtain additive particles of suitable size appear to depend on the first polymer. As the amount of second functional groups increases, the particle size decreases and vice versa. If the amount of second functional groups is too large, particles that are too small are obtained and the second polymer is bound to the first polymer to such an extent that delamination of the first polymer and the absorbent particles is caused. This leads to a decrease in contrast when irradiating an object into which the additive has been mixed in masterbatch form. If the amount of second functional groups is too small, additive particles are obtained that are so large that when irradiating a body into which the additive particles have been mixed in masterbatch form, an inhomogeneous pattern with undesired rough spots forms. In addition, the melt viscosity of the third polymer affects the size of the additive particles in the formed masterbatch. Higher melt viscosity results in smaller particle size. Using the above insights, a person skilled in the art will be able to determine the appropriate amount of the second functional group by simple experimentation, within the upper and lower limits indicated above.

In order to obtain laser-writable polymer compositions, the additives according to the invention are mixed into the matrix polymer. It has been found that the composition of additive and matrix polymer according to the invention can be laser written with better contrast than known compositions, especially if the matrix polymer itself is less laser-writable. Laser writability is also better than when the absorber itself is mixed into the matrix polymer, or only mixed with the first polymer or the second polymer alone.

Accordingly, the present invention also relates to a laser-writable composition comprising a matrix polymer and distributed therein the additive according to the invention.

The advantages of the laser-writable composition according to the invention are fully exhibited in all matrix polymers, however especially in cases where the matrix polymer has been selected from the group consisting of polyethylene, polypropylene, polyamide, polymethyl(meth)acrylate, In the case of polyurethane, polyester thermoplastic vulcanizate (SARLINK(R) is an example), thermoplastic elastomer (Arnitel(R) is an example) or silicone rubber.

The laser-writable composition according to the invention may also contain other additives known to enhance or add properties to the matrix polymer.

Examples of suitable additives for this purpose are reinforcing materials such as glass fibers and carbon fibers, nanofillers such as clays including wollastonite and mica, pigments, dyes and colorants, fillers such as calcium carbonate and talc, processing aids, stabilizers, Antioxidant, Plasticizer, Impact Modifier, Flame Retardant, Release Agent, Blowing Agent.

The amount of these other additives can vary from very small amounts such as 1 or 2 vol. % to 70 or 80 vol. % or more relative to the volume of the compound formed. The additives will generally be used in amounts such that any negative impact on the laser marking contrast obtainable by irradiating the composition will be limited to acceptable levels. Filled compositions exhibiting excellent laser-writability are compositions comprising polyamide, in particular polyamide-6, polyamide-46 or polyamide-66, and talc as filler additive.

Laser-writable compositions according to the invention can be prepared by mixing additives into a molten matrix polymer. To facilitate this mixing, the non-functionalized polymer used as a support in the masterbatch preferably has a melting point lower than or equal to the base polymer. Preferably, the first polymer has a melting point at least equal to or higher than that of the base polymer. The non-functional polymer can be the same as or different from the base polymer. The following description also applies to the first polymer. Accordingly, it has been found that an absorber provided with a layer of polymer composition produces a composition that laser writes with high contrast both when mixed into a polyamide matrix and when mixed into a polyethylene matrix, wherein in the In the above polymer composition, the first polymer is polyamide, and the second polymer is polyethylene grafted with maleic anhydride. This advantageous effect can also be achieved both in polyamides and in polyethylene, if the first polymer is, for example, polycarbonate.

The amount of additive depends on the desired density of the absorbent in the matrix polymer. Typically, the amount of additive is between 0.1 and 10 wt.%, and preferably between 0.5 and 5 wt.%, and more preferably between 1 and 3 wt.%, of the total amount of additive and base polymer. This provides sufficient contrast for most applications without substantially compromising the properties of the base polymer. If dyes are used as additives, it should be considered that it is possible to start with a certain concentration of coloration on the base polymer.

When the additive is mixed into the matrix polymer, the shape of the additive particles may change due to the occurrence of shear force, in particular, they may become longer in shape so as to increase in size. This increase will generally not be greater than a factor of 2, and this can be taken into account when selecting the particle size for incorporation into the matrix polymer, if desired.

The additive-containing base polymer can be processed and shaped using known thermoplastic processing techniques, including foaming. The presence of laser-writable additives will generally not significantly affect the processability of the matrix polymer. In this way, almost any object that can be made from this plastic is available in a laser-writable form. Such objects can be provided, for example, with functional data, barcodes, icons and identification codes, and they can be found in the medical world (syringes, vessels, caps), the motor vehicle business (cables, components), telecommunications and E&E fields (GSM panels, keypads) ), security and identification applications (credit cards, identification plates, labels), advertising applications (icons, cork decorations, golf balls, promotional items) and virtually any other Find applications in areas where objects are useful or desired or effective.

The additive according to the invention can be obtained as described above by mixing the absorbent with a first polymer and then mixing the resulting mixture with a second polymer and optionally an amount of a non-functionalized third polymer. From the resulting three-component mixture, and if the third polymer has also been blended, from the resulting masterbatch, the pure form can be obtained by removing the third polymer and possibly unbound parts of the second polymer from the mixture additives according to the invention. Suitable methods for this are, for example, extraction with a solvent for the second polymer and third polymer (if present) and microfiltration. For isolating the particles in pure form (also denoted minimal particles), it is preferred to use mixtures in which the particle size of the additive is between 500 nm and 20 μm, more preferably between 500 nm and 10 μm, and most preferably between 500 nm and 2 μm or Masterbatch for optimal absorption of laser light and enabling applicability in very thin layers. The smallest particle consists of an additive particle and an outer layer of a second polymer bonded to the first polymer of the additive particle.

It has been found that additives having such a pure minimal particle shape can be applied to surfaces. The powder can be used as such in the form of paint or paint in which the smallest particles are stabilized in a binder. Suitable techniques known per se which can be used for this are, for example, screen printing and offset printing. The resulting surface can then be written on with a laser. The advantage of this method is that the additive need not be present throughout the object and, if desired, can also be applied only where laser-writability is required. Applications can be found in light-coloured painted plastic moldings and, for example, in cards for identification and security applications.

If desired, the applied coating can be covered with a preferably transparent layer to further protect the coating and the pattern written therein later.

The present invention therefore also relates to the application of the additive according to the invention, preferably in the form of the smallest particles, to apply its layer on the surface of an object, and to objects in which a layer comprising the additive according to the invention is at least partially present.

Another suitable form in which the additive according to the invention can be applied, in particular in the form in which the second polymer and if desired the third polymer are present, is a paste or a latex, in which the particles (e.g. the smallest particles) consisting of the additive Or there is a small amount, up to 100% by weight of the total particles, of the smallest particles of the unbound second polymer surrounding them) finely distributed in the dispersion medium that is not the solvent of the second and any third polymer. The additive according to the invention will be composed under high shear in a twin-screw extruder, for example in the presence of a stabilizer known per se to ensure that particles do not settle out of the paste or latex. The particles, preferably the masterbatch of these particles in the third polymer are mixed with a certain amount of dispersion medium to obtain this paste or latex. The ratio between the amount of dispersion medium and the amount of particles or masterbatch determines the viscosity of the resulting mixture. With relatively small amounts of dispersion medium and stabilizer, a paste is obtained, and with relatively large amounts of dispersion medium and stabilizer, a latex is obtained. Water has been found to be a very suitable dispersion medium.

For the production of pastes, the particle size of the additives is preferably chosen between 1 and 200 μm. Preferably, the particle size is between 1 and 90 μm, which has the advantage that when used in coatings, efficient absorption and transparency of laser light can be obtained. For the production of latex, this particle size is preferably between 50 nm and 2 μm, more preferably between 100 nm and 500 nm, making it suitable for use in thin layers. Pastes and latices are suitable for the application of especially aqueous coatings on all surfaces to which they adhere with sufficient force for the intended application. The pastes and latexes according to the invention have been found to adhere particularly well to paper and plastics. In this way, a laser-printable surface can be obtained, for example in a printer provided with a laser having a suitable wavelength without toner, to obtain high-contrast colorfast graphics, such as text or pictures. This fastness provides a major advantage over current paper and printing device combinations. Another advantage, in particular of paper which has been provided with a layer of the paste or latex according to the invention described as being aqueous, is that the paper can be reused in water-based systems. Latex is preferably used as a coating for paper. As a coating of plastic objects, such as dashboard foils, application pastes are preferred.

Another application of the additive according to the invention is obtained by cryogenically grinding the masterbatch of the additive according to the invention in a third polymer, for example, into particles with a size between 100 μm and 1 mm, preferably between 150 and 500 μm the appropriate form. In this form, the additives according to the invention can be mixed into non-melt-processible polymers, such as matrix polymers or crosslinked polymers which degrade near their melting point or have a very high degree of crystallinity. Examples of such matrix polymers are ultrahigh molecular weight polyethylene (UHMWPE), polypropylene oxide (PPO), fluoropolymers such as polytetrafluoroethylene (Teflon), and thermosetting plastics.

The present invention is illustrated based on the following examples.

The following materials were used in the examples and comparative experiments:

As first polymer:

P1-1. Polyamide K122 (DSM)

P1-2. Polycarbonate Xantar(R) R19 (DSM)

P1-3. Polybutylene terephthalate 1060 (DSM)

As a second polymer:

P2-1. Exact(R) polyethylene (DEXPlastomers), grafted with 1.1 wt% MA

P2-2. Fusabond(R) MO525D polyethylene (Dupont), grafted with 0.9 wt% MA

As a third polymer:

P3-1.Exact 0230(R) polyethylene (DEXPlastomers),

P3-2. Propylene-ethylene random copolymer RA112MN40 (DSM)

as absorbent

A-1. Antimony trioxide (Campine) with _{a D50} of 1 μm

A-2. Titanium dioxide

A-3. Macrolex(R) blue/purple

As base polymer:

M-1. Polyamide K122 (DSM)

M-2. Polypropylene homopolymer 112MN40 (DSM)

M-3. Arnitel® EM 400 (DSM)

M-4. Exact(R) 8201 Polyethylene (DSM)

M-5. Sarlink(R) 6135N (DSM)

M-6. Polybutylene terephthalate 1060 (DSM)

M-7.KE 9611U silicone rubber (ShinEtsu)

M-8. UVTRONIC(R) Acrylate Resin (SIPCA)

Examples I-VIII

Using a twin-screw extruder (ZSK 30 from Werner & Pfleiderer), master batches MB1 to MB15 of various additives according to the invention in a third polymer were produced. The absorbent, first and second polymers used in the additive, and the third polymer used and their respective weight percents are shown in Table 1, as are the size and size of the additive particles formed in the masterbatch. Absorbent content.

Using a Haake 350 cc kneader with Banbury kneading arms, MB16 and MB17 were prepared by mixing MB2 with base polymer M7 as the fourth polymer in the amounts given in Table 1, which also shows the final precursor The size of the additive particles formed in feeds M16 and M17.

Master batches MB1-MB15 were produced at an extruder speed of 350-400 rpm with an extrusion rate of 35 kg/h. If polyamide (P1-1) is used as the first polymer, the feed zone, barrel and die temperatures of the extruder and the outlet temperature of the material are 170, 240, 260 and 287°C, respectively. If polycarbonate (P1-2) or PBT (P1-3) was used as the first polymer, then the feed zone, barrel and die temperatures of the extruder and the outlet temperature of the material were 180, 240, 260 and 260°C, respectively. Masterbatches MB16 and MB17 were produced at a temperature of 150°C and a kneader speed of 30-50 rpm.

Table 1

The first polymer The second polymer The third polymer The fourth polymer Absorbent Particle size P1-1 P1-2 P1-3 P2-1 P2-2 P3-1 P3-2 M7 A-1 A-2 A-3 MB2 μm MB1 8 10 40 42 0.1-1.2 MB2 14 1.4 28.6 56 0.2-2 MB3 36 3.6 36.4 twenty four 0.2-2 MB4 42 4.2 25.8 28 0.2-2 MB5 48 4.8 35.2 12 0.2-2 MB6 56 5.6 24.4 14 0.2-2 MB7 12 10 30 48 0.5-1 MB8 14 1.4 28.6 56 0.2-2 MB9 12 10 30 48 MB10 12 7.5 32.5 48 MB11 12 5 35 48 MB12 12 2.5 37.5 48 MB13 32.46 3.2 42.7 21.64 MB14 39.08 3.9 47.26 9.76

The first polymer The second polymer The third polymer The fourth polymer Absorbent particle size P1-1 P1-2 P1-3 P2-1 P2-2 P3-1 P3-2 M7 A-1 A-2 A-3 MB2 µm MB15 25.8 4.2 42 28 MB16 60 40 MB17 50 50

Example II and Comparative Experiment A

Using various masterbatches from the previous examples, various laser-writeable compositions LP1 were prepared by separately mixing different amounts of masterbatch/pigment material into different base polymers on the aforementioned extruder and kneader ~LP41. Compositions comprising PA, PP, Arnitel, Exact, Sarlink and PBT were produced with a ZSK 30 having the feed zone, barrel, die and outlet temperatures of the extruder as given below. Compositions comprising silicone rubber were produced using a Haake kneader with the kneader and outlet temperature given below. In compositions containing acrylate resins, the additives are applied in the form of the smallest particles and the compositions are placed in a Dispermat mixer with the mixing and outlet temperatures given below:

M-1(PA): 160, 200, 220, 265

M-2(PP): 160, 200, 210, 225

M-3 (Arnitel): 160, 200, 220, 237

M-4(Exact): 100, 120, 150, 158

M-5(Sarlink): 160, 180, 220, 225

M-6(PBT): 180, 230, 240, 265

M-7 (silicone rubber): 150, 150

M-8 (acrylate resin): 20, 60

Table 2 gives the weight percentages of the different components.

The resulting composition was injection molded to form a 2 mm thick plate. Patterns were written on the board using a Lasertec diode-pumped Nd:YAG UV laser with a wavelength of 355 nm and a Trumpf, Vectomark Compact diode-pumped Nd:YAG IR laser with a wavelength of 1064 nm.

For comparison, under the conditions as given above, from compositions containing only the third polymer (CP-A to CP-G) and many polymers that have been polymerized by mixing only the absorbent masterbatch in polyamide to the matrix Compositions (CP-H to CP-M) prepared in the compound were also prepared in a similar plate and written at a temperature of that of the masterbatch or the matrix polymer, whichever has a higher melting point than the polymer in the masterbatch things.

Table 2 shows the degree of laser writability of different materials expressed in qualitative contrast values. Contrast was measured using a Minolta 3700D spectrophotometer with the following settings: CIELAB, light source 6500 Kelvin (D65), including spectral color (spec colourincluded, SCI) and measurement angle 10°. At the wavelengths used of 355nm and 1064nm, the laser settings were continuously optimized up to the maximum feasible contrast.

As can be seen from the results, writing with a laser on a plate made of a material comprising the additive according to the invention is more effective than writing in which there is no absorber or in which the application is mixed only to the first and third polymers (in this case equal to the first polymer). ) compositions of absorbent masterbatches, much better results can be obtained.

Figure 1 shows a TEM image of the laser-writable composition LP7.

Table 2

combination masterbatch masterbatch A-1: Antimony trioxide M-1: PA M-2: PP M-3: Amitel M-4: Exact M-5: Sarlink M-6: PBT M-7: Silicone rubber Contrast 355nm Contrast 1064nm MB1 MB2 LP1 10 4.2 90 ····· ····· LP2 10 4.2 90 ····· ····· LP3 10 4.2 90 ····· ····· LP4 10 4.2 90 ····· ····· LP5 10 4.2 90 ····· ····· LP6 5 2.8 95 ····· ····· LP7 5 2.8 95 ····· ····· LP8 5 2.8 95 ····· ····· LP9 5 2.8 95 ····· ····· LP10 5 2.8 95 ····· ····· LP11 3 1.68 97 ····· ····· LP12 3 1.68 97 ····· ····· LP13 3 1.68 97 ····· ····· LP14 3 1.68 97 ····· ·····

combination masterbatch masterbatch A-1: Antimony trioxide M-1: PA M-2: PP M-3: Arntel M-4: Exact M-5: Sarlink M-6: PBT M-7: Silicone rubber Contrast 355nm Contrast 1064nm LP15 3 1.68 97 ····· ····· LP16 1 0.56 99 ··· ··· LP17 1 0.56 99 ··· ··· LP18 1 0.56 99 ···· ··· LP19 1 0.56 99 ··· ··· LP20 1 0.56 99 ··· ··· LP21 3 1.68 97 ····· ····· LP22 2 1.12 98 ····· ····· LP23 1 0.56 99 ····· ····· LP24 0.5 0.28 99.5 ····· ···· MB8 MB12 LP25 10 4.2 90 ····· ····· LP26 5 2.8 95 ····· ····· LP27 3 1.68 97 ····· ····· LP28 2 1.12 98 ····· ····· LP29 1 0.56 99 ···· ···· LP30 2 0.96 98 ····· ·····

combination masterbatch masterbatch A-1: Antimony trioxide M-1: PA M-2: PP M-3: Amitel M-4: Exact M-5: Sarlink M-6: PBT M-7: Silicone rubber Contrast 355nm Contrast 1064nm MB13 MB14 LP31 5 1.082 95 ····· ····· LP32 3 0.649 97 ···· ···· LP33 11 1.074 89 ···· ···· LP34 7.5 0.733 92.5 ··· ··· MB15 MB17 LP35 5 1.4 95 ····· - LP36 3 0.84 97 ····· - LP37 2 0.56 98 ···· - LP38 1 0.28 99 ···· - LP39 10 2.8 90 ····· ····· LP40 5 1.4 95 ····· ····· LP41 3 0.84 97 ····· ····· CP-A 100 · · CP-B 100 - - -C 100 · ·

combination masterbatch masterbatch A-1: Antimony trioxide M-1: PA M-2: PP M-3: Amitel M-4: Exact M-5: Sarlink M-6: PBT M-7: Silicone rubber Contrast 355nm Contrast 1064nm -D 100 - - -E 100 · · -F 100 · · -G 100 - - CP-H 0.8 99.2 · ·· -I 0.8 0.2 99 - · -J 0.8 0.2 99 · · -K 0.8 0.2 99 - · -L 0.8 0.2 99 · · -M 0.8 0.2 99 · ···

Quality of contrast:

Very poor contrast and grainy -

poor contrast ·

Moderate Contrast · ·

good contrast ···

very good contrast ····

Excellent Contrast Ratio ·····

Example III

In the two masterbatches MB2 and MB15, the additive particles consisting respectively of the first polymer P1-1 and the absorbent A-1 and the first polymers P1-1 and A-2 were separated from the third polymer. To this end, masterbatches MB15 and MB2 were dissolved in decahydronaphthalene in an autoclave at 140-145° C. and separated at this temperature by centrifugation. The additive particles obtained were distributed in an acrylate resin (UVTRONIC(R) from SICPA) at concentrations of 20, 10 and 5 wt.%, stabilized with Disperbyk(R) from (BYK). The resulting mixture was coated on a polyester support by lithography. Compositions with additive particles obtained from MB2 are referred to as LP42-LP44, compositions with additive particles obtained from MB15 are referred to as LP45-LP47, these series of compositions contain 20, 10 and 5 wt.% of additive particles respectively .

The degree of laser writability of the different materials was determined as in Example II for wavelengths 355 and 1064 nm, and is shown in Table 3, expressed as qualitative contrast values.

table 3

combination Matrix polymer absorbent absorbent first polymer wavelength M-8: Acrylic resin A-1 A-2 P1-1 355 1064 LP42 80 16 4 ····· ····· LP43 90 8 2 ···· ···· LP44 95 4 1 ·· ·· LP45 80 8 12 ····· -

LP46 90 4 6 ···· - LP47 95 2 3 ··· -

Claims (18)

1. A laser absorbing additive comprising particles comprising at least a first polymer having a first functional group and 0 to 95% by weight of an absorber, said weight percentage being relative to the total amount of said first polymer and said absorber , in at least a portion of the particle surface, the first polymer is bound through the first functional group to a second functional group bound to a second polymer. 2. The additive of claim 1, wherein the second functional group has been grafted onto the second polymer. 3. The additive of claim 1, wherein the first functional group is an end group of the first polymer. 4. The additive of claim 1, wherein the second polymer is a polyolefin. 5. The additive of claim 1, wherein the first polymer has a degree of carbonization of at least 5%. 6. An additive according to any one of claims 1 to 5, wherein a third polymer is also present. 7. The additive of claim 1 comprising at least 1 wt% absorbent. 8. A method of preparing a laser absorbing additive according to any one of claims 1 to 7, comprising combining a composition comprising an absorber and a first polymer having a first functional group with a polymer comprising a polymer reactive with said first functional group A second polymer with a second functional group is mixed. 9. The method of claim 8, wherein a third polymer is present during the mixing operation. 10. Laser-writable composition comprising a matrix polymer and distributed therein the additive according to any one of claims 1 to 7 or produced by a process according to one of claims 8 to 9. 11. The laser-writable composition according to claim 10, wherein 0.1 to 10 wt.% of the compound according to any one of claims 1 to 8 or by the method according to any one of claims 9 to 11 is present. prepared additives. 12. The laser-writable composition according to claim 11, wherein 0.5 to 5 wt.% of the additive is present. 13. The laser-writable composition according to claim 12, wherein 1 to 3 wt.% of additives are present. 14. Object whose surface is provided with a laser-writable layer comprising at least an additive according to claim 1. 15. The object of claim 14, at least 80% of the surface of the object consists of a polymer. 16. The object of claim 14, the surface of which consists essentially of paper. 17. Paste or latex comprising the additive according to claim 1 in a dispersion medium. 18. The paste or latex according to claim 17, wherein the dispersion medium is water.

Images