Nitrile preforms and containers and process improvements for forming same
AssigneeMonsanto Company
InventorsMorris Salame, Samuel Steingiser
Life of this patent
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Abstract
In forming containers by distending preforms of nitrile thermoplastic material at molding temperature, the improvement comprising exposing such preforms to low dosage radiation to reduce residual nitrile monomer in the thermoplastic material and then distending the irradiated preforms to cause HCN generated during irradiation to flash off in forming the container. The containers formed have unusually low concentrations of residual nitrile monomer as well as extractable HCN making them especially suitable for packaging foods, beverages, pharmaceuticals and the like. The irradiated preforms from which such containers are made have similarly low residual nitrile monomer levels.
Claims48
In the process of forming containers from preforms of thermoplastic material comprising at least about 20 weight percent of polymerized nitrile-group-containing monomer which includes distending the preforms while at molding temperature into containers in a mold,
- the improvement which comprises:
- exposing the preforms to low dosage electron beam radiation prior to said distending;
- whereby said radiation causes polymerization of unpolymerized nitrile-group-containing monomer and said distending causes HCN generated during such irradiation to be reduced in the thermoplastic material.
In the process of forming containers for environmentally sensitive materials from preforms of thermoplastic material comprising at least 20 weight percent of polymerized nitrile-group-containing monomer which includes distending the preforms while at blow molding temperature into the containers in a mold,
- the improvement minimizing unpolymerized nitrile-group-containing monomer and extractable HCN in the walls of the containers which comprises:
- distending irradiated preforms containing no greater than about 1.5 ppm of unpolymerized nitrile-group-containing monomer based on the weight of total polymer in the cavity of a mold into container form whereby said HCN is reduced without increasing said unpolymerized monomer.
In the process of forming containers for foods, beverages, pharmaceuticals and the like from tubular preforms comprising a major proportion of polymerized nitrile-group-containing monomer which includes distending the preforms while at molding temperature into the containers in a mold,
- the improvement wherein unpolymerized nitrile-group-containing monomer and extractable HCN in the walls of the containers are reduced which comprises:
- distending irradiated preforms containing (a) no greater than about 1.5 ppm unpolymerized nitrile-group-containing monomer based on the total weight of the polymer and (b) a detectable extractable HCN content, in the cavity of a mold into container form whereby said HCN content is reduced without increasing said unpolymerized monomer.
An irradiated preform for conversion into a container for environmentally sensitive materials, said preform being formed of a thermoplastic material comprising at least 20 weight percent of a polymerized nitrile-group-containing monomer and an effective amount of an HCN scavenger, the level of unpolymerized nitrile monomer in such preform being no greater than about 1.5 ppm based on the total weight of the polymer.
A container for environmentally sensitive materials formed of an irradiated thermoplastic material comprising at least 20 weight percent of a polymerized nitrile-group-containing monomer, said container having levels of unpolymerized nitrile monomer and extractable HCN of no greater than about 0.8 ppm based on the total weight of the polymer and about 50 ppb based on extracting liquid respectively.
Dependencies are inferred from the claim text.