Method of and composition for producing a resoluble barrier coating against moist vapoure for use as flexible packaging material
9 claims: 2 independent, 7 dependent
- 1Zastrzeżenia patentowe 1. Kompozycja zapewniająca zdolną do ponownego roztworzenia powłokę barierową dla par wilgoci przeznaczoną na elastyczne opakowania, znamienna tym, że zawiera:emulsję polimeru o rozdziale wielkości cząstek drobniejszą niż 10 μ, przy czym polimer ten jest wybrany z grupy obejmującej polichlorek winylidenu, metakrylan metylu i akrylonitryl oraz mieszaniny tych polimerów;i dodatek stanowiący ziarnisty materiał o średniej wielkości cząstek mniejszej niż 10 μ, zdolny do międzywęzłowego wiązania się z cząstkami polimeru dając powłokę na elastycznym materiale opakowaniowym, która zabezpiecza właściwości barierowe dla pary wilgoci zapewniane przez ten polimer i która po ponownym roztworzeniu rozdrabnia się na kawałki mniejsze niż 1,6 mm, przy czym materiał ziarnisty wybrany jest z grupy obejmującej uwodniony krzemian glinowy, węglan wapniowy, homopolimer polioctanu winylu i ich mieszaniny;przy czym odczyn pH tej kompozycji wynosi 2-8.
- 2Kompozycja według zastrz. 1, znamienna tym, że emulsja polimeru zawiera polichlorek winylidenu.
- 3Kompozycja według zastrz. 1, znamienna tym, że dodatek stanowi zawiesinę uwodnionego krzemianu glinowego, a pH tej kompozycji jest następnie doprowadzone do wartości mniejszej niż 2.
- 4Kompozycja według zastrz. 1, znamienna tym, że dodatek zawiera węglan wapniowy, a pH wynosi 6-7.
- 5Kompozycja według zastrz. 1, znamienna tym, że dodatek zawiera homopolimer polioctanu winylu, a pH wynosi 2,0.
- 6Kompozycja według zastrz. 1, znamienna tym, że zawiera:emulsję polimeru zawierającą polichlorek winylidenu, w której polichlorek winylidenu wykazuje średni rozdział wielkości cząstek drobniejszy niż 10 μ;oraz dodatek zawierający emulsję cząstek uwodnionego krzemianu glinowego o średnim rozdziale wielkości cząstek drobniejszym niż 10 μ;przy czym odczyn pH tej kompozycji wynosi 2,0.
- 7Kompozycja według zastrz. 1, znamienna tym, że zawiera:emulsję polimeru zawierającą polichlorek winylidenu, w której polichlorek winylidenu wykazuje średni rozdział wielkości cząstek drobniejszy niż 10 μ;oraz dodatek zawierający rozdrobniony węglan wapniowy o średnim rozdziale wielkości cząstek drobniejszym niż 10 μ;przy czym odczyn pH tej kompozycji wynosi 6,0.
- 8Kompozycja według zastrz. 1, znamienna tym, że dodatek ponadto zawiera polioctan winylu o zasadniczo tym samym rozdziale wielkości cząstek co węglan wapniowy.
- 9Sposób ponownego przetwarzania elastycznego papierowego materiału opakowaniowego pokrytego powłoką barierową dla par wilgoci, przez rozdrobnienie materiału opakowaniowego na włókna składowe i cząstki wspomnianej powłoki, znamienny tym, że materiał opakowaniowy zawierający powłokę składającą się z mieszaniny polichlorku winylidenu i dodatku w postaci ziarnistej, zdolnego do międzywęzłowego wiązania się z cząstkami polichlorku winylidenu, dającej powłokę na elastycznym papierowym materiale opakowaniowym, zabezpieczającą właściwości barierowe dla pary wilgoci, rozdrabniania się na cząstki, których 185 362 co najmniej 95% jest mniejszych niż 1,6 mm, otrzymane cząstki przesiewa się i oddziela większe niż 1,6 mm i z pozostałych cząstek sporządza się masę papierniczą.
Independent claims9
99 paragraphs, as filed
The subject of the invention is a composition providing a reproducible moisture vapor barrier coating for flexible packaging and a method for reprocessing flexible paper packaging material coated with a moisture barrier coating. More specifically, the invention relates to a method of re-processing a packaging flexible material having a moisture vapor barrier coating thereon, in which the coating is mixed with cellulose fibers and a pulp is obtained, the fibers being adapted to be reconstituted with pulp. The composition according to the invention is intended for the production of flexible packaging, which is provided by a coating that allows re-processing into valuable paper products.
Current practice is to add a polyethylene coating, a wax coating or a polyvinylidene chloride (PVDC) coating on a paper substrate or between two sheets of paper, with the paper substrate and sheets of paper being referred to as layers to provide a flexible package that is moisture and vapor barrier. At present, it is believed that all moisture barrier coatings cannot be reconstituted.
Other resins are also used to provide flexible packaging materials with low moisture and vapor permeability, such as polyacrylates, polyvinyl acetate, and the like. However, to achieve the same barrier, they are more expensive than wax, polyethylene and polyvinylidene chloride coatings.
Moisture barrier coatings that are present in moisture barrier packaging materials are considered by paper mills to be recycled (reconstituted) unsuitable for reconstitution, mainly because they introduce quality problems in the fiber recovery method, or by process disturbance (clogging of the screen) or contamination of the final product.
Currently, more than 20% of all paper and cardboard produced in the world, as indicated above, is laminated, resulting in products that are incompatible with the recycling industry.
One disadvantage of polyethylene, wax or PVDC coated packaging is that it is difficult to recycle or recycle and must usually be discarded. Removing moisture barrier packaging materials has become an important problem for paper mills and their customers. Recycling (recycling) these materials causes particular problems for this industry. The moisture barrier presents a challenge to recover useful fibers from these packaging materials, and many recycling mills are unable to overcome the problem of re-diluting them. Currently, almost all moisture barrier packaging materials are placed on waste leveled areas and are not reconstituted.
On the other hand, the reprocessing of wood fiber based packaging is an important source of wood fiber. In addition, due to the abovementioned difficulties, these materials usually have to be rejected, which is unacceptable according to current environmental protection views. The reprocessing of wood-based packaging is an increasingly important source of wood fibers, and the waste of high-quality and expensive fibers can no longer be tolerated because these fibers account for millions of tons of waste materials.
There are normally two ways to reprocess wood fibers. The first method involves shredding a source of wood fibers, such as those present in the packaging material, into forming fibers as a result of re-pulping, while any other material is screened with ordinary equipment. The second method involves shredding the package in such a way that any additional material, such as a coating, will be crushed to smaller pieces smaller than 1.6 mm. which will be
185 362 walk through a sieve with pulp fibers. The latter method is normally carried out using additional equipment and / or chemicals, which makes it very expensive.
Unfortunately, none of the prior art wax-containing or wax-free resins that are used to provide coatings for flexible packaging cannot be reprocessed without additional processing steps, making reprocessing difficult. In addition, the presence of wax in the moisture and vapor barrier coating reduces the usability of the resulting pulp and therefore the amount of waste increases.
In the pulping process, the wax barriers are broken up into very small particles (smaller than 0.7 mm), which pass through the screen and are finally in the pulp, which is sent to a paper machine as well as in sieved water. The problems associated with reconstitution of wax-based barriers are as follows:
- wax particles clog the felt;
- wax particles coat the rubber tumble dryer causing the paper to tear;
- wax is deposited on the surface of the manufactured product, which causes problems during printing and causes sticking of the final product; and
- reducing the usefulness of the pulp obtained.
On the other hand, when polyethylene is used as the vapor barrier coating, when reconstituted, crushed into large pieces of a thin layer, whose length is in the range of about 0.3 cm to 2.5 cm. Polyethylene causes the screen to clog, requires cleaning time and produces solid waste.
The problems associated with polyvinylidene chloride barrier coatings are generally the same as those found when the barrier coatings are made of polyethylene.
Because PVDC has the advantage of providing a coating that is an excellent vapor barrier, a good oxygen barrier, as well as having chemical resistance properties at a relatively low price, it would be economically advantageous for the production of paper rolls or similar products suitable for flexible packaging, including PVDC coatings that would be suitable for complete recycling or reprocessing.
However, in the current state of the art, any attempt to modify the reconstitution capability of PVDC and other types of resins, by adding materials or treating packaging to increase the hardness of the thin layer, would lead to a huge loss of barrier properties, which of course are not acceptable.
Coatings based on PVDC are known, for example, see British Patent No. UK-1583947, published February 4, 1981, inventor Federic Douglas Hough. However, these coatings are used on paper to make reprint sheets. This patent is silent about the recycling of this coated paper and does not give any guidance on the production of a coating that could be re-reconstituted with paper fibers.
British Patent No. UK-2039789 published on August 10, 1980, inventor Adrian Neville Fellows, describes the preparation of a dielectric coating from a dispersion of an electrotechnical polymer and water-dispersible smectic clay. There is no information in this description to provide a coating that is characterized by being vapor-impermeable, suitable for reconstitution when it is crushed to a pulp mixture.
Richard M. Podhajny in 'The search for alternative moisture-barrier coatings', Converting Magazine®, August 1995, suggests that alternatives to PVDC are urgently needed because of the environmental contaminating nature of PVDC when this polymer is allowed to enter in the waste stream. Although PVDC coatings, with or without additives, are known, it will seem that a suitable solution in which the coating will remain in the pulp during recycling and therefore will not pollute the environment has not yet been achieved.
B. Alince and P. Lepoutre in the publication TAPPI Journal, vol. 66, No. 11, pp. 57 and 58 revealed that the viscosity of aqueous suspensions is improved at low shear by using clay, calcium carbonate and latex, which could be polystyrene.
185 362
Japanese Patent No. JP-A-06136698 discloses a paper substrate made of wood pulp and a barrier layer containing, as a binder, PVDC latex. The publication of international application WO 93/13264 generally discloses a layered material comprising a thermoplastic polymer such as PVDC latex and an additive which could be talc and / or silica with filling and / or bleaching properties.
International Patent Application Publication No. WO 93/13264 discloses a coating material for use in coating a plastic material or fibrous material, the coating material comprising an additive that gives improved "coating properties" to the coating material. Example 7 of this application discloses a composition that contains 100 parts PVDC, 24 parts talc (<10 pm) (hydrated magnesium silicate) and 0.7 parts pH adjusting agent. Thus, other components are used in the solution of WO 93/13264. In addition, tests carried out with a barrier coating according to this solution have shown that although it has good coating properties, it is not suitable for re-pulping.
With the current amount of paper used, it will not be possible to maintain the traditional speed of paper source delivery from forests, and means will have to be found to obtain sufficient fiber that meets the requirements.
The invention relates to a composition providing a re-dissolving moisture vapor barrier coating for flexible packaging, which according to the invention comprises:
a polymer emulsion with a particle size distribution smaller than 10 μ, wherein the polymer is selected from the group consisting of polyvinylidene chloride, methyl methacrylate and acrylonitrile, and mixtures of these polymers; and an additive consisting of a granular material with an average particle size of less than 10 μ, capable of interstitial bonding with polymer particles giving a coating on flexible packaging material that protects the moisture vapor barrier properties provided by this polymer and which, when reconstituted, crumbles into smaller pieces than 1.6 mm, the granular material is selected from the group consisting of hydrated aluminum silicate, calcium carbonate, polyvinyl acetate homopolymer and mixtures thereof; wherein the pH of this composition is 2-8.
In the composition of the invention, preferably, the polymer emulsion comprises polyvinylidene chloride.
In the composition of the invention, preferably, the additive is a suspension of hydrated aluminum silicate, and the pH of this composition is then adjusted to less than 2.
In the composition of the invention, preferably, the additive comprises calcium carbonate and the pH is 6-7.
Preferably, in the composition of the invention, the additive comprises polyvinyl acetate homopolymer and the pH is 2.0.
The composition according to the invention preferably comprises:
a polymer emulsion containing polyvinylidene chloride in which the polyvinylidene chloride has an average particle size distribution of less than 10 μ; and an additive comprising an emulsion of hydrated aluminum silicate particles having an average particle size distribution less than 10 μ;
wherein the pH of this composition is 2.0.
The composition according to the invention preferably comprises:
a polymer emulsion containing polyvinylidene chloride in which the polyvinylidene chloride has an average particle size distribution of less than 10 μ; and an additive containing ground calcium carbonate with an average particle size distribution less than 10 μ;
wherein the pH of this composition is 6.0.
Preferably, in the composition of the invention, the additive further comprises polyvinyl acetate with substantially the same particle size distribution as calcium carbonate.
185 362
The method of reprocessing flexible paper packaging material covered with a moisture and vapor barrier coating by crushing the packaging material into constituent fibers and particles of said coating, according to the invention, is that the packaging material comprising a coating consisting of a mixture of polyvinylidene chloride and an additive in granular form, capable of interstitial binding to polyvinylidene chloride particles, coating on flexible paper packaging material that protects moisture vapor barrier properties, is divided into particles of which at least 95% is smaller than 1.6 mm, the obtained particles are sieved and separated larger than 1.6 mm, and the remaining particles are prepared paper pulp.
Thus, it is an object of the invention to provide a modified, reproducible, moisture barrier and vapor barrier film of polyvinylidene, intended for flexible packaging, which would give recyclable and screenable packaging and which provide an excellent moisture and vapor barrier and a barrier to oxygen, exhibit excellent chemical resistance properties and that provide excellent bond strength to paper laminate.
The invention provides a modified, reducible polyvinylidene chloride coating, which is applied to a paper or cardboard layer, provides a suitable moisture and vapor barrier and which does not interfere with the re-pulping process using a paper machine or in the final product.
According to the subject matter of the invention there is provided a modified, reducible polyvinylidene chloride coating which, once reconstituted, will be crumbled into small pieces, preferably smaller than 1.6 mm, and will fiberize very easily, thus minimizing the number of shortcomings.
According to the subject of the present invention, there is provided a moisture and vapor barrier coating which, when ground, gives particles that will pass through the screen and be dispersed with the fibers.
The invention provides a modified, reducible polyvinylidene chloride coating that does not produce solid recycled waste that does not dissolve in the aqueous process and does not contribute to BOD (biological oxygen consumption) in the wastewater, and which produces particles that are inert and do not reactivate by heating.
The invention provides an economically feasible, modified, reducible barrier coating, such as a PVDC based coating, which has essentially the same barrier properties and at least almost the same adhesion to paper as unmodified barrier coatings, and which moreover is easily recovered , suitable for reconstitution at a low cost.
The invention provides a coating composition for flexible packaging having improved current rheology, which improves flow properties and protects the coating against penetration into the pores of the paper, such as for the currently used low shear viscosity of PVDC.
The invention provides a barrier coating that does not require the use of comprehensive equipment that implies the associated chemical treatment when primary fibers are recovered.
The invention provides a flexible barrier coating that can be laminated onto a layer of paper substrate without using glue.
According to the invention, a composition providing a barrier for moisture and vapor able to re-solubilize the flexible packaging material, which comprises an emulsion polymer with a particle size distribution finer than 10 μ and a supplement which is a particulate material having an average particle size of about 10 μ, which is capable y for interstitial bonding with polymer particles giving a coating on flexible packaging material, which protects the moisture and vapor barrier properties provided by this polymer and which, when reconstituted, breaks into pieces generally smaller than about 1.6 mm. The pH of the composition should be such that it allows the coating to comminute to pieces generally smaller than 1.6 mm.
185 362
According to the invention, there is also provided a method of reprocessing flexible, paper packaging material covered with a moisture and vapor barrier coating, which consists in that said packaging material is crushed into constituent fibers and particles of said coating. The method according to the invention consists in that the coating comprises a mixture containing polyvinylidene chloride and an additive in particulate form, which is capable of interstitial bonding with the particles of said polyvinylidene chloride and gives a coating on said flexible paper packaging material that protects moisture and vapor barrier properties provided by polyvinylidene chloride. The method involves crushing the packaging material containing the coating into particles of which at least 95% is generally less than 1.6 mm, sieving and separating particles larger than 1.6 mm, and making the pulp into remaining particles.
Although many polymers can be used to make the barrier coating of the invention, as is well known to those skilled in the art, preferred polymers include polyvinylidene chloride, methyl methacrylate and acrylonitrile, and mixtures thereof.
Similarly, with respect to the adhesive, hydrated aluminum silicate, calcium carbonate, polyvinyl acetate homopolymer and mixtures thereof are preferred.
In practice, the most interesting polymer emulsion contains polyvinylidene chloride.
The preferred polymer in the polymer emulsion is polyvinylidene chloride (PVDC), which is an excellent moisture barrier, since its molecular structure is capable of providing crystalline areas in which the polymer chains align and arrange in an orderly manner. As discussed in "The Search for Alternative Moisture-Barrier Coatings," Converting Magazine®, August 1995, strong and interacting bonds form in these chains. Interactions between H and Cl atoms are responsible for the strong attraction between PVDC chains, the formation of dense, three-dimensional crystal lattices.
When re-pulping in a standard crusher, the mechanical forces applied to the coating are not sufficient to break the bonds between these chains and produce particles smaller than 1.6 mm, because the particles obtained are generally larger than 6 mm.
By adding selected additives to PVDC, such as hydrated aluminum silicate and calcium carbonate with an average particle size distribution of less than about 10 μ, and selection of a critical pH, crystallinity still remains in the composition, but smaller particles become possible to produce by grinding additives.
As mentioned above, the pH of the solution is critical. For example, with hydrated aluminum silicate, the pH must generally be lower than or equal to about 2. For calcium carbonate, the pH should normally be between 6 and 7.
Of course, too high a concentration of additives would quickly reduce the moisture resistance of the created vapor barrier. It has been found that particles of the desired good quality can still be produced when polyvinyl acetate is used as the additive. This additive is not as good as hydrated aluminum silicate or calcium carbonate to provide a mixture capable of good reconstitution, however, it has less negative effect on the vapor barrier impermeability. On the other hand, the combined use of polyvinyl acetate and calcium carbonate gives excellent results in terms of repulpability and impermeability. Other additives that give satisfactory results include polystyrene emulsions, polyacrylates, etc.
The invention is illustrated by the accompanying drawings, it being understood that the invention is not limited to these drawings. In the drawing: figure 1 shows paper obtained using fresh cellulose fibers; Figure 2 - Paper obtained by re-opening a flexible package having a vapor barrier according to the invention; Fig. 3 - the paper as in Fig. 1, in which the vapor barrier is PVDC; and Fig. 4 - the paper as in Fig. 1, in which the vapor barrier is polyethylene.
185 362
It can easily be seen that, in practice, the coating known from the prior art is not able to re-dissolve, and the present invention provides paper that is substantially equivalent to that made from fresh fibers.
The invention is illustrated by the following examples:
Example 1
The coating composition was prepared by mixing 80 parts of polyvinylidene chloride emulsion sold under the trade name SERFENE 2022 with 20 parts of a hydrated aluminum silicate suspension sold under the trade name OMNIFIL. The pH of the mixture containing 54.5% solid was adjusted to 2.1 and a coating was formed on the flexible paper packaging product using this mixture. By reconstituting the coated product, the product was ground to smaller particles than 1.5 mm, which in practice allows all coatings to be re-digested.
MVTR (moisture vapor transmission rate, 100% RH (relative humidity, 37.8 ° C), 25% g / m<sup>2</sup> coating on the cardboard layer: 15 g / m2<sup>2</sup>/day.
Example 2
Example 1 was repeated, except that OMNIFIL was replaced by 10 parts of calcium carbonate sold under the trade name PULPRO 3 and 10 parts of polyvinyl acetate homopolymer sold under the trade name DARATACK 7IL. The pH was adjusted to 6.2. The mixture contained 55.7% solids. Re-digestion gave particles smaller than 1.2 mm.
MVTR: 4 g / m2 / day
Example 3
Example 1 was repeated, except that 66 parts of SERFENE 2022 with 27 parts of DARAN SLI 12®, which is a copolymer of vinylidene chloride, methyl methacrylate and acrylonitrile, and 7 parts of DARATACK 7IL were used. The pH was adjusted to 2.1. The mixture contained 51.5% solids. Re-digestion gave particles smaller than 1.5 mm.
Example 4
Example 1 was repeated except that 85 parts of SERFENE 2022 with 15 parts of DARATACK 7IL were used. The pH was adjusted to pH 2.1 and the mixture contained 50.8% solids. Re-reconstitution gave particles smaller than 1.5 mm, which allow all coatings to be reconstituted.
MVTR: 4 g / m2 / day
Example 5
Example 1 was repeated, except that 75 parts of SERFENE 2022 with 15 parts of PULpRo 8 (trade name for ground calcium carbonate slightly thicker than PULPRO 3) and 10 parts of DARATACK 7IL were used. The pH was adjusted to 6.2 and the mixture contained 58% solids, reconstitution gave particles smaller than 1.5 mm.
MVTR: 8 g / m2 / day.
Example 6
Example 1 was repeated, except that 75 parts of SERFENE 2022 and 11 parts of PULpRo 8 and 14 parts of LYTRON 604 (trade name of emulsion particles of a homogeneous, hard, light, spherical polystyrene polymer) were used. The mixture was adjusted to pH 6.1 and the mixture contained 54% solids. Re-digestion gave particles smaller than 1.6 mm.
MVTR: 5 g / m2<sup>2</sup>/day.
All of the above examples show that the particles are equivalent to fresh fibers, which means that they can be easily reprocessed and that the moisture vapor transmission rate is in practice equivalent to PVDC.
Tests carried out with the paper coated with the composition according to the invention show that, reconstitution gives about 97% of particles smaller than 1.6 mm after 30 minutes of dissolution.
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Of course, modifications are possible that will be readily available to those skilled in the art without departing from the scope and spirit of the present invention, except those defined in the appended claims.
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Priority claims8
| Document | Office | Kind | Date |
|---|---|---|---|
| 37598895 | United States of America | A | |
| 37598895 | United States of America | A | |
| 9600033 | Canada | W | |
| 9600033 | Canada | W | |
| 95375988 | – | – | – |
| 96CA9600033 | – | – | – |
| US19950375988 | – | – | – |
| WO1996CA00033 | – | – | – |
Members34
| Document | Office | Kind | |
|---|---|---|---|
| CA2210984A1 | Canada | A1 | |
| WO9622329A1 | World Intellectual Property Organization (WIPO) | A1 | |
| AU4428896A | Australia | A | |
| NO973329D0 | Norway | D0 | |
| NO973329L | Norway | L | |
| FI973061A | Finland | A | |
| FI973061A7 | Finland | A7 | |
| FI973061L | Finland | L | |
| EP0804505A1 | European Patent Office (EPO) | A1 | |
| BR9607090A | Brazil | A | |
| PL321497A1 | Poland | A1 | |
| MX9705526A | Mexico | A | |
| HU9801118A2 | Hungary | A2 | |
| HUP9801118A2 | Hungary | A2 | |
| NZ298730A | New Zealand | A | |
| AU704224B2 | Australia | B2 | |
| EP0804505B1 | European Patent Office (EPO) | B1 | |
| AT180814T | Austria | T | |
| ATE180814T1 | Austria | T1 | |
| DE69602718D1 | Germany | D1 | |
| US5929155A | United States of America | A | |
| ES2136969T3 | Spain | T3 | |
| DK0804505T3 | Denmark | T3 | |
| DE69602718T2 | Germany | T2 | |
| GR3031145T3 | Greece | T3 | |
| RU2158284C2 | Russian Federation | C2 | |
| US6150451A | United States of America | A | |
| CA2210984C | Canada | C | |
| NO311364B1 | Norway | B1 | |
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| PL185362B1This record | Poland | B1 | |
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Numbers
- Publication, DOCDB
- 185362
- Publication, EPODOC
- PL185362B
- Application
- 96321497
- Application, DOCDB
- 32149796
- Application, EPODOC
- PL19960321497
Titles2
- English
- METHOD OF AND COMPOSITION FOR PRODUCING A RESOLUBLE BARRIER COATING AGAINST MOIST VAPOURE FOR USE AS FLEXIBLE PACKAGING MATERIAL
- Polish
- Kompozycja zapewniająca zdolną do ponownego roztworzenia powłokę barierową dla par wilgoci przeznaczoną na elastyczne opakowania i sposób ponownego przetwarzania elastycznego papierowego materiału opakowaniowego pokrytego powłoką barierową dla par wilgoci
Classification
- CPC, 6
- D21H19/20
- C08L25/10
- C08L27/08
- C08L31/04
- D21C5/02
- Y02W30/64
- IPC, 8
- C09D127 08
- B65D65 42
- C08L25 10
- C08L27 08
- C08L31 04
- D21C5 02
- D21H19 20
- D21H19 58
